diff --git a/apps/web/src/app/(portal)/page.tsx b/apps/web/src/app/(portal)/page.tsx
index ad9523c..a4d6279 100644
--- a/apps/web/src/app/(portal)/page.tsx
+++ b/apps/web/src/app/(portal)/page.tsx
@@ -5,6 +5,8 @@ import { useTranslations } from 'next-intl';
 import { DashboardGrid } from '@/components/dashboard/dashboard-grid';
 import { DashboardTabs } from '@/components/dashboard/dashboard-tabs';
 import { EditModeToggle } from '@/components/dashboard/edit-mode-toggle';
+import { BackgroundPicker, DashboardBackdrop, useDashboardBackground } from '@/components/dashboard/dashboard-background';
+import { useAuthStore } from '@/lib/stores/auth-store';
 import { WidgetCatalogModal } from '@/components/dashboard/widget-catalog-modal';
 import { registerWidget } from '@/components/dashboard/widget-registry';
 import { ClockWidget } from '@/components/dashboard/widgets/clock-widget';
@@ -45,6 +47,10 @@ interface ActiveModule {
 export default function DashboardPage() {
   const t = useTranslations('widgets');
   const [catalogOpen, setCatalogOpen] = useState(false);
+  // Hintergrund je Benutzer (Design „Mosaik“, Prototyp mit localStorage).
+  const userId = useAuthStore((s) => s.user?.id);
+  const { background, choose: chooseBackground } = useDashboardBackground(userId);
+  const hasBackground = background.kind !== 'none';
   // quick-260922-m1h: Slugs der Module, die dieser Benutzer nutzen darf —
   // der Katalog blendet Kacheln gesperrter Module damit aus. `null` heisst
   // "noch unbekannt oder Abruf fehlgeschlagen" und ist fail-closed.
@@ -115,7 +121,8 @@ export default function DashboardPage() {
   }
 
   return (
-    <div className="relative p-2">
+    <div className={`relative p-2 ${hasBackground ? 'dashboard-has-bg' : ''}`}>
+      <DashboardBackdrop background={background} />
       {/* Reiterleiste (quick-260923-ad9) — seit quick-260924-h7x per Portal
           in der Kopfzeile, hier nimmt sie keinen Platz mehr ein. Sie bleibt
           waehrend eines Reiterwechsels stehen, nur das Raster zeigt eine
@@ -151,11 +158,12 @@ export default function DashboardPage() {
           Grid direkt unter der Kopfzeile beginnt (12 + 8 + 8 = 28 px statt 60 px).
           Im Bearbeitungsmodus steht "Widget hinzufuegen" links neben dem Haekchen. */}
       <div className="fixed bottom-6 right-6 z-20 flex items-center gap-2">
+        {isEditMode && <BackgroundPicker value={background} onChange={chooseBackground} />}
         {isEditMode && (
           <button
             type="button"
             onClick={() => setCatalogOpen(true)}
-            className="flex items-center gap-2 rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground shadow-lg hover:opacity-90 transition-opacity"
+            className="btn btn-primary shadow-lg"
           >
             <svg
               aria-hidden="true"
diff --git a/apps/web/src/components/dashboard/dashboard-background.tsx b/apps/web/src/components/dashboard/dashboard-background.tsx
new file mode 100644
index 0000000..3b1663c
--- /dev/null
+++ b/apps/web/src/components/dashboard/dashboard-background.tsx
@@ -0,0 +1,276 @@
+'use client';
+
+import { useTranslations } from 'next-intl';
+import { useTheme } from 'next-themes';
+import { type CSSProperties, useCallback, useEffect, useRef, useState } from 'react';
+import {
+  BACKGROUND_PRESETS,
+  type DashboardBackground,
+  loadDashboardBackground,
+  NO_BACKGROUND,
+  presetBackground,
+  saveDashboardBackground,
+} from '@/lib/dashboard-background';
+import {
+  type DashboardImageMeta,
+  dashboardImageSrc,
+  fetchDashboardImages,
+  uploadDashboardImage,
+} from '@/lib/dashboard-images-api';
+
+/** Wahl des Hintergrunds fuer den angemeldeten Benutzer (localStorage, Prototyp). */
+export function useDashboardBackground(userId: string | null | undefined) {
+  const [background, setBackground] = useState<DashboardBackground>(NO_BACKGROUND);
+
+  useEffect(() => {
+    if (userId) setBackground(loadDashboardBackground(userId));
+  }, [userId]);
+
+  const choose = useCallback(
+    (value: DashboardBackground) => {
+      setBackground(value);
+      if (userId) saveDashboardBackground(userId, value);
+    },
+    [userId],
+  );
+
+  return { background, choose };
+}
+
+/** CSS fuer eine Wahl; Flaechenfarbe oder Bild, jeweils bildschirmfuellend. */
+function backgroundStyle(value: DashboardBackground, dark: boolean): CSSProperties | null {
+  if (value.kind === 'none') return null;
+  if (value.kind === 'image') {
+    return {
+      backgroundImage: `url("${dashboardImageSrc(value.imageId)}")`,
+      backgroundSize: 'cover',
+      backgroundPosition: 'center',
+    };
+  }
+  const css = presetBackground(value.id, dark);
+  if (!css) return null;
+  return css.startsWith('url(')
+    ? { backgroundImage: css, backgroundSize: 'cover', backgroundPosition: 'center' }
+    : { backgroundColor: css };
+}
+
+/**
+ * Bildschirmfuellende Hintergrundebene hinter dem Dashboard. Liegt fest
+ * unter Kopfzeile und Seitenleiste (beide haben eigene Flaechen). Im dunklen
+ * Erscheinungsbild werden eigene Bilder abgedunkelt — so bleibt der Text auf
+ * den durchscheinenden Kacheln auch bei einem sehr hellen Foto lesbar.
+ */
+export function DashboardBackdrop({ background }: { background: DashboardBackground }) {
+  const { resolvedTheme } = useTheme();
+  const dark = resolvedTheme === 'dark';
+  const style = backgroundStyle(background, dark);
+  if (!style) return null;
+  return (
+    <div
+      aria-hidden="true"
+      data-testid="dashboard-backdrop"
+      data-background={background.kind === 'preset' ? background.id : background.kind}
+      className={`pointer-events-none fixed inset-0 z-0 ${
+        background.kind === 'image' ? 'dark:brightness-[0.55]' : ''
+      }`}
+      style={style}
+    />
+  );
+}
+
+interface BackgroundPickerProps {
+  value: DashboardBackground;
+  onChange: (value: DashboardBackground) => void;
+}
+
+function sameChoice(a: DashboardBackground, b: DashboardBackground): boolean {
+  if (a.kind !== b.kind) return false;
+  if (a.kind === 'preset' && b.kind === 'preset') return a.id === b.id;
+  if (a.kind === 'image' && b.kind === 'image') return a.imageId === b.imageId;
+  return true;
+}
+
+/**
+ * Knopf „Hintergrund“ (nur im Bearbeitungsmodus) mit einem kleinen Fenster:
+ * Vorschaubilder fuer „Keiner“, die eingebauten Hintergruende, die eigenen
+ * Bilder und eine Kachel zum Hochladen eines neuen Bildes.
+ */
+export function BackgroundPicker({ value, onChange }: BackgroundPickerProps) {
+  const t = useTranslations('dashboard.background');
+  const { resolvedTheme } = useTheme();
+  const dark = resolvedTheme === 'dark';
+  const [open, setOpen] = useState(false);
+  const [images, setImages] = useState<DashboardImageMeta[] | null>(null);
+  const [uploading, setUploading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const rootRef = useRef<HTMLDivElement>(null);
+  const fileRef = useRef<HTMLInputElement>(null);
+
+  useEffect(() => {
+    if (!open || images !== null) return;
+    fetchDashboardImages()
+      .then(setImages)
+      .catch(() => setImages([]));
+  }, [open, images]);
+
+  useEffect(() => {
+    if (!open) return;
+    function onPointer(e: MouseEvent) {
+      if (rootRef.current && !rootRef.current.contains(e.target as Node)) setOpen(false);
+    }
+    function onKey(e: KeyboardEvent) {
+      if (e.key === 'Escape') setOpen(false);
+    }
+    document.addEventListener('mousedown', onPointer);
+    document.addEventListener('keydown', onKey);
+    return () => {
+      document.removeEventListener('mousedown', onPointer);
+      document.removeEventListener('keydown', onKey);
+    };
+  }, [open]);
+
+  async function handleUpload(file: File | undefined) {
+    if (!file) return;
+    setError(null);
+    setUploading(true);
+    try {
+      const meta = await uploadDashboardImage(file);
+      setImages((prev) => [meta, ...(prev ?? [])]);
+      onChange({ kind: 'image', imageId: meta.id });
+    } catch (e) {
+      setError(e instanceof Error ? e.message : t('uploadError'));
+    } finally {
+      setUploading(false);
+      if (fileRef.current) fileRef.current.value = '';
+    }
+  }
+
+  const option = (
+    key: string,
+    label: string,
+    choice: DashboardBackground,
+    preview: CSSProperties,
+    content?: React.ReactNode,
+  ) => {
+    const selected = sameChoice(value, choice);
+    return (
+      <li key={key}>
+        <button
+          type="button"
+          onClick={() => onChange(choice)}
+          aria-pressed={selected}
+          title={label}
+          className="group flex w-full flex-col items-stretch gap-1 rounded-md text-left focus-visible:outline-none"
+        >
+          <span
+            className={`flex h-12 items-center justify-center overflow-hidden rounded-md border text-muted-foreground transition-shadow group-focus-visible:ring-2 group-focus-visible:ring-ring ${
+              selected ? 'border-transparent ring-2 ring-foreground' : 'border-border group-hover:border-input-strong'
+            }`}
+            style={preview}
+          >
+            {content}
+          </span>
+          <span className={`truncate text-xs ${selected ? 'font-semibold text-foreground' : 'text-muted-foreground'}`}>
+            {label}
+          </span>
+        </button>
+      </li>
+    );
+  };
+
+  return (
+    <div ref={rootRef} className="relative">
+      <button
+        type="button"
+        onClick={() => setOpen((v) => !v)}
+        aria-expanded={open}
+        aria-haspopup="dialog"
+        className="btn btn-secondary shadow-lg"
+      >
+        <svg aria-hidden="true" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+          <rect x="3" y="3" width="18" height="18" rx="2" />
+          <circle cx="9" cy="9" r="2" />
+          <path d="m21 15-3.1-3.1a2 2 0 0 0-2.8 0L6 21" />
+        </svg>
+        {t('button')}
+      </button>
+
+      {open && (
+        <div
+          role="dialog"
+          aria-label={t('title')}
+          className="absolute bottom-full right-0 z-30 mb-2 w-[min(22rem,calc(100vw-2rem))] rounded-lg bg-card p-4 text-card-foreground shadow-xl dark:border dark:border-border"
+        >
+          <h2 className="text-sm font-semibold">{t('title')}</h2>
+          <p className="mt-0.5 text-xs text-muted-foreground">{t('hint')}</p>
+
+          <h3 className="mt-4 text-xs font-semibold text-muted-foreground">{t('builtIn')}</h3>
+          <ul className="mt-2 grid grid-cols-3 gap-3">
+            {option('none', t('none'), NO_BACKGROUND, { backgroundColor: 'var(--background)' },
+              <svg aria-hidden="true" xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.75" strokeLinecap="round"><circle cx="12" cy="12" r="8" /><path d="m6.5 17.5 11-11" /></svg>,
+            )}
+            {BACKGROUND_PRESETS.map((preset) => {
+              const css = dark ? preset.dark : preset.light;
+              return option(
+                preset.id,
+                t(`presets.${preset.labelKey}`),
+                { kind: 'preset', id: preset.id },
+                css.startsWith('url(')
+                  ? { backgroundImage: css, backgroundSize: 'cover', backgroundPosition: 'center' }
+                  : { backgroundColor: css },
+              );
+            })}
+          </ul>
+
+          <h3 className="mt-4 text-xs font-semibold text-muted-foreground">{t('ownImages')}</h3>
+          <ul className="mt-2 grid max-h-40 grid-cols-3 gap-3 overflow-y-auto p-0.5">
+            {(images ?? []).map((image) =>
+              option(
+                image.id,
+                image.originalName,
+                { kind: 'image', imageId: image.id },
+                {
+                  backgroundImage: `url("${dashboardImageSrc(image.id)}")`,
+                  backgroundSize: 'cover',
+                  backgroundPosition: 'center',
+                },
+              ),
+            )}
+            <li>
+              <button
+                type="button"
+                onClick={() => fileRef.current?.click()}
+                disabled={uploading}
+                className="group flex w-full flex-col items-stretch gap-1 rounded-md text-left focus-visible:outline-none"
+              >
+                <span className="flex h-12 items-center justify-center rounded-md border border-dashed border-input-strong text-muted-foreground transition-colors group-hover:bg-muted group-hover:text-foreground group-focus-visible:ring-2 group-focus-visible:ring-ring">
+                  {uploading ? (
+                    <span className="inline-block h-4 w-4 animate-spin rounded-full border-2 border-current border-t-transparent" />
+                  ) : (
+                    <svg aria-hidden="true" xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round"><path d="M12 5v14" /><path d="M5 12h14" /></svg>
+                  )}
+                </span>
+                <span className="truncate text-xs text-muted-foreground">{t('upload')}</span>
+              </button>
+            </li>
+          </ul>
+          <input
+            ref={fileRef}
+            type="file"
+            accept="image/png,image/jpeg,image/webp,image/gif"
+            className="hidden"
+            onChange={(e) => handleUpload(e.target.files?.[0])}
+          />
+          {images !== null && images.length === 0 && (
+            <p className="mt-2 text-xs text-muted-foreground">{t('noImages')}</p>
+          )}
+          {error && (
+            <p role="alert" className="mt-2 text-xs text-destructive">
+              {error}
+            </p>
+          )}
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/apps/web/src/components/dashboard/dashboard-grid.test.tsx b/apps/web/src/components/dashboard/dashboard-grid.test.tsx
index 2220bff..43fc340 100644
--- a/apps/web/src/components/dashboard/dashboard-grid.test.tsx
+++ b/apps/web/src/components/dashboard/dashboard-grid.test.tsx
@@ -165,7 +165,7 @@ describe('DashboardGrid', () => {
     expect(document.querySelector('.widget-drag-handle')).toBeInTheDocument();
   });
 
-  it('quick-260916-bwo Test 4: Grid-Props — 24/20/12/8/2 Spalten, rowHeight 20, margin 8, Breakpoints unveraendert, containerPadding folgt dem margin', async () => {
+  it('quick-260916-bwo Test 4: Grid-Props — 24/20/12/8/2 Spalten, rowHeight 20, margin 12, Breakpoints unveraendert, containerPadding folgt dem margin', async () => {
     captured.props = null;
     const { DashboardGrid } = await import('./dashboard-grid');
     render(
@@ -181,7 +181,7 @@ describe('DashboardGrid', () => {
     expect(captured.props).not.toBeNull();
     expect(captured.props?.cols).toEqual({ lg: 24, md: 20, sm: 12, xs: 8, xxs: 2 });
     expect(captured.props?.rowHeight).toBe(20);
-    expect(captured.props?.margin).toEqual([8, 8]);
+    expect(captured.props?.margin).toEqual([12, 12]);
     expect(captured.props?.breakpoints).toEqual({ lg: 1200, md: 996, sm: 768, xs: 480, xxs: 0 });
     expect(captured.props?.containerPadding).toBeUndefined();
   });
diff --git a/apps/web/src/components/dashboard/dashboard-grid.tsx b/apps/web/src/components/dashboard/dashboard-grid.tsx
index 854921e..2d15867 100644
--- a/apps/web/src/components/dashboard/dashboard-grid.tsx
+++ b/apps/web/src/components/dashboard/dashboard-grid.tsx
@@ -229,7 +229,7 @@ export function DashboardGrid({
         cols={COLS}
         layouts={effectiveLayouts as ResponsiveLayouts}
         rowHeight={20}
-        margin={[8, 8] as [number, number]}
+        margin={[12, 12] as [number, number]}
         // containerPadding bewusst nicht gesetzt: react-grid-layout 2.2.3 nimmt
         // dann das margin (gemessen: effectiveContainerPadding = containerPadding ?? margin).
         dragConfig={{
diff --git a/apps/web/src/components/dashboard/dashboard-tabs.tsx b/apps/web/src/components/dashboard/dashboard-tabs.tsx
index a66068e..8a09a6d 100644
--- a/apps/web/src/components/dashboard/dashboard-tabs.tsx
+++ b/apps/web/src/components/dashboard/dashboard-tabs.tsx
@@ -507,7 +507,7 @@ export function DashboardTabs({
             role="alertdialog"
             aria-modal="true"
             aria-label={t('tabs.deleteDialogTitle')}
-            className="relative z-[60] mx-4 max-w-md rounded-lg border border-border bg-card p-6 shadow-xl"
+            className="relative z-[60] mx-4 max-w-md rounded-lg bg-card dark:border dark:border-border p-6 shadow-xl"
           >
             <h3 className="mb-2 text-lg font-semibold text-foreground">
               {t('tabs.deleteDialogTitle')}
diff --git a/apps/web/src/components/dashboard/edit-mode-toggle.tsx b/apps/web/src/components/dashboard/edit-mode-toggle.tsx
index 54ab702..b730592 100644
--- a/apps/web/src/components/dashboard/edit-mode-toggle.tsx
+++ b/apps/web/src/components/dashboard/edit-mode-toggle.tsx
@@ -21,11 +21,7 @@ export function EditModeToggle({ isEditMode, onToggle }: EditModeToggleProps) {
     <button
       type="button"
       onClick={onToggle}
-      className={`inline-flex items-center justify-center rounded-md p-2 shadow-lg transition-colors ${
-        isEditMode
-          ? 'bg-primary text-primary-foreground hover:opacity-90'
-          : 'border border-border bg-card text-muted-foreground hover:bg-muted hover:text-foreground'
-      }`}
+      className={`btn btn-icon h-10 w-10 shadow-lg ${isEditMode ? 'btn-primary' : 'btn-secondary text-muted-foreground'}`}
       aria-pressed={isEditMode}
       aria-label={isEditMode ? t('saveChanges') : t('editMode')}
       title={isEditMode ? t('saveChanges') : t('editMode')}
diff --git a/apps/web/src/components/dashboard/widgets/calculator-widget.tsx b/apps/web/src/components/dashboard/widgets/calculator-widget.tsx
index f137571..fe7e700 100644
--- a/apps/web/src/components/dashboard/widgets/calculator-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/calculator-widget.tsx
@@ -313,7 +313,7 @@ export function CalculatorWidget({ isEditMode }: WidgetProps) {
   // Klassen stehen woertlich als Literale, damit der Tailwind-Scanner sie findet.
   const baseBtn = 'h-full min-h-7 cursor-pointer select-none active:scale-95';
   const numBtn = `${baseBtn} bg-background hover:bg-muted border border-border text-foreground text-[clamp(11px,min(4cqw,4.5cqh),40px)]`;
-  const opBtn = `${baseBtn} bg-muted hover:bg-muted/80 border border-border text-primary font-semibold text-[clamp(11px,min(4cqw,4.5cqh),40px)]`;
+  const opBtn = `${baseBtn} bg-muted hover:bg-muted/80 border border-border text-foreground font-semibold text-[clamp(11px,min(4cqw,4.5cqh),40px)]`;
   const utilBtn = `${baseBtn} bg-muted/50 hover:bg-muted border border-border text-muted-foreground text-[clamp(10px,min(3.2cqw,3.6cqh),32px)]`;
   const eqBtn = `${baseBtn} bg-primary hover:bg-primary/90 text-primary-foreground font-semibold text-[clamp(11px,min(4cqw,4.5cqh),40px)]`;
   // Speicherzeile bleibt bewusst klein (h-7 text-xs) — Nebenfunktion, kein Hauptinhalt.
diff --git a/apps/web/src/components/dashboard/widgets/calendar-widget.tsx b/apps/web/src/components/dashboard/widgets/calendar-widget.tsx
index fb4a596..4aa6cb2 100644
--- a/apps/web/src/components/dashboard/widgets/calendar-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/calendar-widget.tsx
@@ -243,21 +243,21 @@ export function CalendarWidget({ config }: WidgetProps) {
   const hoverEvents = hover ? (eventsByDate.get(hover.key) ?? []) : [];
 
   return (
-    <div className="flex h-full flex-col gap-1 overflow-hidden p-1.5">
+    <div className="flex h-full flex-col gap-2 overflow-hidden p-3">
       {showMonth && (
         <div data-testid="calendar-month" className="flex shrink-0 flex-col gap-1">
           {/* Nav-Zeile */}
           <div className="grid grid-cols-[1fr_1.4fr_1fr] gap-1">
             <button
               type="button"
-              className="widgetNoDrag rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-foreground hover:bg-muted"
+              className="widgetNoDrag rounded-md px-1 py-[clamp(3px,0.9cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-muted-foreground transition-colors hover:bg-muted hover:text-foreground"
               onClick={showPrev}
             >
               {t('calendar.monthPrev')}
             </button>
             <button
               type="button"
-              className="widgetNoDrag truncate rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] font-semibold leading-none text-foreground hover:bg-muted"
+              className="widgetNoDrag truncate rounded-md px-1 py-[clamp(3px,0.9cqh,6px)] text-[clamp(11px,2.8cqw,14px)] font-semibold leading-none text-foreground transition-colors hover:bg-muted"
               title={t('calendar.monthToday')}
               onClick={showToday}
             >
@@ -265,7 +265,7 @@ export function CalendarWidget({ config }: WidgetProps) {
             </button>
             <button
               type="button"
-              className="widgetNoDrag rounded border border-border bg-muted/50 px-1 py-[clamp(2px,0.8cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-foreground hover:bg-muted"
+              className="widgetNoDrag rounded-md px-1 py-[clamp(3px,0.9cqh,6px)] text-[clamp(10px,2.6cqw,13px)] leading-none text-muted-foreground transition-colors hover:bg-muted hover:text-foreground"
               onClick={showNext}
             >
               {t('calendar.monthNext')}
@@ -286,9 +286,9 @@ export function CalendarWidget({ config }: WidgetProps) {
               const badges = buildDayBadges(day.events);
               const single = badges.length === 1;
               const cellClass = [
-                'widgetNoDrag relative flex min-h-[clamp(16px,5.5cqh,40px)] items-start rounded bg-muted/50 px-1 py-0.5 text-[clamp(9px,2.4cqw,13px)] leading-none',
-                day.inCurrentMonth ? 'text-foreground' : 'text-muted-foreground/60',
-                day.isToday ? 'ring-1 ring-primary font-semibold text-primary' : '',
+                'widgetNoDrag relative flex min-h-[clamp(16px,5.5cqh,40px)] items-start rounded-md px-1 py-0.5 text-[clamp(9px,2.4cqw,13px)] leading-none',
+                day.inCurrentMonth ? 'text-foreground' : 'text-muted-foreground/70',
+                day.isToday ? 'bg-primary font-semibold text-primary-foreground' : '',
                 hasEvents ? 'cursor-default hover:bg-muted' : '',
               ]
                 .filter(Boolean)
@@ -405,7 +405,7 @@ export function CalendarWidget({ config }: WidgetProps) {
           ) : (
             <ul data-testid="calendar-upcoming" className="min-h-0 flex-1 space-y-1 overflow-y-auto">
               {upcoming.map((event) => (
-                <li key={event.id} className="flex items-start gap-2 rounded bg-muted/50 px-2 py-1">
+                <li key={event.id} className="flex items-start gap-2 rounded-md px-2 py-1 hover:bg-muted">
                   <span
                     data-testid="event-color-dot"
                     className="mt-1 h-2 w-2 shrink-0 rounded-full"
@@ -416,7 +416,7 @@ export function CalendarWidget({ config }: WidgetProps) {
                     <p className="truncate text-[clamp(9px,2.2cqw,12px)] text-muted-foreground">
                       {formatEventDate(event)}
                     </p>
-                    <p className="truncate text-[clamp(10px,2.5cqw,14px)] font-semibold text-foreground">
+                    <p className="truncate text-[clamp(10px,2.5cqw,14px)] font-medium text-foreground">
                       {event.title}
                     </p>
                     {event.location && (
@@ -438,7 +438,7 @@ export function CalendarWidget({ config }: WidgetProps) {
           <div
             data-testid="calendar-day-tooltip"
             role="tooltip"
-            className="pointer-events-none fixed z-50 rounded border border-border bg-card p-2 text-xs text-foreground shadow-lg"
+            className="pointer-events-none fixed z-50 rounded bg-card dark:border dark:border-border p-2 text-xs text-foreground shadow-lg"
             style={{
               width: TOOLTIP_WIDTH_PX,
               top: hover.rect.bottom + TOOLTIP_EDGE_PX,
diff --git a/apps/web/src/components/dashboard/widgets/favorites-widget.tsx b/apps/web/src/components/dashboard/widgets/favorites-widget.tsx
index 786f519..5947af1 100644
--- a/apps/web/src/components/dashboard/widgets/favorites-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/favorites-widget.tsx
@@ -321,7 +321,7 @@ export function FavoritesWidget({
     <div className="flex h-full flex-col overflow-hidden">
       {/* Header: optional title (quick-260916-iex) — mirrors note-widget.tsx look */}
       {showHeader && (
-        <div className="flex items-center gap-2 border-b border-border px-1.5 py-1.5">
+        <div className="widget-head">
           {isEditMode ? (
             <input
               type="text"
@@ -341,7 +341,7 @@ export function FavoritesWidget({
         </div>
       )}
 
-      <div className="flex flex-1 flex-col gap-2 overflow-auto p-1">
+      <div className={`flex flex-1 flex-col gap-2 overflow-auto px-2 pb-2 ${showHeader ? '' : 'pt-2'}`}>
       {/* View mode toggle (edit mode only) */}
       {isEditMode && (
         // role="toolbar" (D-03): die bisherige Beschriftung ("Favoriten")
@@ -359,8 +359,8 @@ export function FavoritesWidget({
             onClick={() => handleViewMode('list')}
             className={`px-2 py-1 text-xs rounded ${
               viewMode === 'list'
-                ? 'bg-primary text-primary-foreground'
-                : 'bg-muted text-muted-foreground'
+                ? 'bg-foreground text-background'
+                : 'bg-muted text-muted-foreground hover:text-foreground'
             }`}
           >
             {t('favorites.listView')}
@@ -370,8 +370,8 @@ export function FavoritesWidget({
             onClick={() => handleViewMode('grid')}
             className={`px-2 py-1 text-xs rounded ${
               viewMode === 'grid'
-                ? 'bg-primary text-primary-foreground'
-                : 'bg-muted text-muted-foreground'
+                ? 'bg-foreground text-background'
+                : 'bg-muted text-muted-foreground hover:text-foreground'
             }`}
           >
             {t('favorites.gridView')}
@@ -675,7 +675,7 @@ function FavoriteTile({
           href={fav.url}
           target="_blank"
           rel="noreferrer"
-          className="flex items-center gap-2 flex-1 min-w-0 hover:underline widgetNoDrag"
+          className="flex h-8 min-w-0 flex-1 items-center gap-2.5 rounded-md px-1.5 transition-colors hover:bg-muted widgetNoDrag"
           onClick={(e) => isEditMode && e.preventDefault()} // block navigation in edit mode
         >
           {/* Icon container with letter fallback (T-08-07 — no dangerouslySetInnerHTML) */}
@@ -685,7 +685,7 @@ function FavoriteTile({
             getFallbackLetter={getFallbackLetter}
           />
 
-          <span className="text-xs truncate">{fav.title}</span>
+          <span className="truncate text-sm">{fav.title}</span>
         </a>
 
         {/* Action buttons (edit mode only, D-04) */}
diff --git a/apps/web/src/components/dashboard/widgets/note-widget.tsx b/apps/web/src/components/dashboard/widgets/note-widget.tsx
index 23bbee1..35d4874 100644
--- a/apps/web/src/components/dashboard/widgets/note-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/note-widget.tsx
@@ -163,7 +163,7 @@ export function NoteWidget({ instanceId, config }: WidgetProps) {
   return (
     <div className="flex h-full flex-col overflow-hidden" data-color-mode={colorMode}>
       {/* Header: title + pencil toggle */}
-      <div className="relative flex items-center border-b border-border px-1.5 py-1.5 gap-2">
+      <div className="widget-head relative">
         <input
           type="text"
           className="flex-1 bg-transparent text-sm font-semibold text-foreground outline-none placeholder:text-muted-foreground"
@@ -180,7 +180,7 @@ export function NoteWidget({ instanceId, config }: WidgetProps) {
         <button
           type="button"
           onClick={() => setIsEditing((v) => !v)}
-          className={`flex h-6 w-6 shrink-0 items-center justify-center rounded transition-colors hover:bg-muted ${isEditing ? 'text-destructive' : 'text-muted-foreground'}`}
+          className={`widget-action flex h-7 w-7 shrink-0 items-center justify-center rounded-md transition-colors hover:bg-muted ${isEditing ? 'widget-action-pinned bg-muted text-foreground' : 'text-muted-foreground hover:text-foreground'}`}
           title={isEditing ? t('note.viewMode') : t('note.editMode')}
         >
           <svg
@@ -203,7 +203,7 @@ export function NoteWidget({ instanceId, config }: WidgetProps) {
 
       {/* Content: preview or editor */}
       <div
-        className="flex-1 overflow-auto"
+        className="widget-note-body flex-1 overflow-auto"
         data-testid="note-preview"
         ref={previewRef}
       >
diff --git a/apps/web/src/components/dashboard/widgets/proxmox-widget.tsx b/apps/web/src/components/dashboard/widgets/proxmox-widget.tsx
index 1b1d572..a6d85d5 100644
--- a/apps/web/src/components/dashboard/widgets/proxmox-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/proxmox-widget.tsx
@@ -162,7 +162,7 @@ export function ProxmoxWidget({ instanceId, config, isEditMode }: WidgetProps) {
   let header: ReactNode = null;
   if (isEditMode) {
     header = (
-      <div className="flex shrink-0 items-center gap-2 border-b border-border px-2.5 py-1.5">
+      <div className="widget-head">
         <input
           type="text"
           className="widgetNoDrag min-w-0 flex-1 bg-transparent text-sm font-semibold text-foreground outline-none placeholder:text-muted-foreground"
@@ -186,7 +186,7 @@ export function ProxmoxWidget({ instanceId, config, isEditMode }: WidgetProps) {
     );
   } else if (trimmedTitle !== '') {
     header = (
-      <div className="shrink-0 border-b border-border px-2.5 py-1.5">
+      <div className="widget-head">
         <h2 className="truncate text-sm font-semibold text-foreground">{trimmedTitle}</h2>
       </div>
     );
diff --git a/apps/web/src/components/dashboard/widgets/search-widget.tsx b/apps/web/src/components/dashboard/widgets/search-widget.tsx
index 6daeca1..209479d 100644
--- a/apps/web/src/components/dashboard/widgets/search-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/search-widget.tsx
@@ -113,7 +113,7 @@ export function SearchWidget({ instanceId, config }: WidgetProps) {
       {/* Search button (right) */}
       <button
         type="button"
-        className="flex h-8 shrink-0 items-center justify-center rounded bg-primary px-3 text-sm font-medium text-primary-foreground transition-colors hover:bg-primary/90"
+        className="btn btn-primary shrink-0"
         onClick={handleSearch}
         aria-label={t('search.searchButton')}
       >
diff --git a/apps/web/src/components/dashboard/widgets/widget-wrapper.tsx b/apps/web/src/components/dashboard/widgets/widget-wrapper.tsx
index c6f1500..4a89154 100644
--- a/apps/web/src/components/dashboard/widgets/widget-wrapper.tsx
+++ b/apps/web/src/components/dashboard/widgets/widget-wrapper.tsx
@@ -30,9 +30,11 @@ export function WidgetWrapper({ widget, isEditMode, onRemove }: WidgetWrapperPro
   const definition = WIDGET_REGISTRY[widget.widgetType as WidgetType];
   const WidgetComponent = definition?.component;
 
+  // Design „Mosaik“: in der Ansicht eine ruhige Fluent-Karte (hell Schatten,
+  // dunkel Haarlinie), die Akzent-Umrandung nur im Bearbeitungsmodus.
   const cardClassName = isEditMode
-    ? 'widget-drag-handle relative h-full w-full cursor-grab overflow-hidden rounded-lg border border-primary/40 bg-card shadow-sm active:cursor-grabbing'
-    : 'relative h-full w-full overflow-hidden rounded-lg border border-primary/20 bg-card shadow-sm';
+    ? 'widget-drag-handle relative h-full w-full cursor-grab overflow-hidden rounded-lg bg-card shadow-md active:cursor-grabbing'
+    : 'relative h-full w-full overflow-hidden rounded-lg bg-card shadow-sm dark:border dark:border-border';
 
   return (
     <article
@@ -45,7 +47,7 @@ export function WidgetWrapper({ widget, isEditMode, onRemove }: WidgetWrapperPro
           Hoehenkette Karte -> Rumpf bleibt definit (cqh loest weiter auf). */}
       {isEditMode && (
         <div
-          className="absolute inset-x-0 top-0 z-10 flex h-5 items-center justify-center bg-muted/70"
+          className="absolute inset-x-0 top-0 z-10 flex h-5 items-center justify-center bg-muted/80"
           title={t('dragHint')}
           data-testid="widget-drag-head"
         >
diff --git a/apps/web/src/components/dashboard/widgets/xframe-widget.test.tsx b/apps/web/src/components/dashboard/widgets/xframe-widget.test.tsx
index 261441c..2f9d19c 100644
--- a/apps/web/src/components/dashboard/widgets/xframe-widget.test.tsx
+++ b/apps/web/src/components/dashboard/widgets/xframe-widget.test.tsx
@@ -84,12 +84,12 @@ describe('XframeWidget (quick-260921-qd3)', () => {
     expect(link.className).toContain('absolute');
   });
 
-  it('Test 5: mit Titel -> <h2> Board, <iframe title="Board">, Link in der Kopfleiste (Vorfahre border-b), nicht absolute', () => {
+  it('Test 5: mit Titel -> <h2> Board, <iframe title="Board">, Link in der Kopfleiste (Vorfahre widget-head), nicht absolute', () => {
     const { container } = renderWidget({ url: URL_A, title: 'Board' });
     expect(container.querySelector('h2')).toHaveTextContent('Board');
     expect(frame().getAttribute('title')).toBe('Board');
     const link = screen.getByRole('link', { name: 'xframe.openInNewTab' });
-    expect(link.closest('.border-b')).not.toBeNull();
+    expect(link.closest('.widget-head')).not.toBeNull();
     expect(link.className).not.toContain('absolute');
   });
 
diff --git a/apps/web/src/components/dashboard/widgets/xframe-widget.tsx b/apps/web/src/components/dashboard/widgets/xframe-widget.tsx
index 783395d..71cfe82 100644
--- a/apps/web/src/components/dashboard/widgets/xframe-widget.tsx
+++ b/apps/web/src/components/dashboard/widgets/xframe-widget.tsx
@@ -119,12 +119,12 @@ export function XframeWidget({ config, isEditMode }: WidgetProps) {
         // Bekannt und akzeptiert (wie die Titelzeile der Favoriten): im
         // Bearbeitungsmodus ueberdeckt die 20-px-Griffleiste der Karte den
         // oberen Teil der Kopfleiste — Bearbeiten ist Anordnen, nicht Lesen.
-        <div className="flex items-center gap-2 border-b border-border px-1.5 py-1.5">
+        <div className="widget-head">
           <h2 className="min-w-0 flex-1 truncate text-sm font-semibold text-foreground">{title}</h2>
           <NewTabLink
             url={url}
             label={openLabel}
-            className="shrink-0 rounded p-0.5 text-muted-foreground hover:text-foreground"
+            className="widget-action shrink-0 rounded-md p-1 text-muted-foreground hover:bg-muted hover:text-foreground"
           />
         </div>
       )}
diff --git a/apps/web/src/lib/dashboard-background.test.ts b/apps/web/src/lib/dashboard-background.test.ts
new file mode 100644
index 0000000..3d88bc5
--- /dev/null
+++ b/apps/web/src/lib/dashboard-background.test.ts
@@ -0,0 +1,54 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import {
+  BACKGROUND_PRESETS,
+  loadDashboardBackground,
+  presetBackground,
+  saveDashboardBackground,
+} from './dashboard-background';
+
+afterEach(() => {
+  window.localStorage.clear();
+  vi.restoreAllMocks();
+});
+
+describe('dashboard-background (Design „Mosaik“, Prototyp)', () => {
+  it('ohne gespeicherte Wahl: kein Hintergrund', () => {
+    expect(loadDashboardBackground('u1')).toEqual({ kind: 'none' });
+  });
+
+  it('speichert je Benutzer getrennt', () => {
+    saveDashboardBackground('u1', { kind: 'preset', id: 'bloom' });
+    saveDashboardBackground('u2', { kind: 'image', imageId: 'img-1' });
+    expect(loadDashboardBackground('u1')).toEqual({ kind: 'preset', id: 'bloom' });
+    expect(loadDashboardBackground('u2')).toEqual({ kind: 'image', imageId: 'img-1' });
+  });
+
+  it('verwirft kaputte oder unbekannte Werte', () => {
+    window.localStorage.setItem('tessera.dashboardBackground.u1', '{kaputt');
+    expect(loadDashboardBackground('u1')).toEqual({ kind: 'none' });
+    window.localStorage.setItem(
+      'tessera.dashboardBackground.u1',
+      JSON.stringify({ kind: 'preset', id: 'regenbogen' }),
+    );
+    expect(loadDashboardBackground('u1')).toEqual({ kind: 'none' });
+  });
+
+  it('gesperrter Speicher wirft nicht', () => {
+    vi.spyOn(Storage.prototype, 'getItem').mockImplementation(() => {
+      throw new Error('blocked');
+    });
+    vi.spyOn(Storage.prototype, 'setItem').mockImplementation(() => {
+      throw new Error('blocked');
+    });
+    expect(() => saveDashboardBackground('u1', { kind: 'preset', id: 'mist' })).not.toThrow();
+    expect(loadDashboardBackground('u1')).toEqual({ kind: 'none' });
+  });
+
+  it('jeder eingebaute Hintergrund hat eine helle und eine dunkle Fassung', () => {
+    for (const preset of BACKGROUND_PRESETS) {
+      expect(presetBackground(preset.id, false)).toBeTruthy();
+      expect(presetBackground(preset.id, true)).toBeTruthy();
+      expect(presetBackground(preset.id, false)).not.toBe(presetBackground(preset.id, true));
+    }
+  });
+});
diff --git a/apps/web/src/lib/dashboard-background.ts b/apps/web/src/lib/dashboard-background.ts
new file mode 100644
index 0000000..a40fadb
--- /dev/null
+++ b/apps/web/src/lib/dashboard-background.ts
@@ -0,0 +1,142 @@
+/**
+ * Dashboard-Hintergrund (Prototyp, Design „Mosaik“).
+ *
+ * Wahl je Benutzer: kein Hintergrund, ein eingebauter (ruhige Flaechen und
+ * drei abstrakte Motive in gedaempften Modulfarben — keine Regenbogen-
+ * verlaeufe) oder ein eigenes Bild aus den Bilderrahmen-Bildern
+ * (`/dashboard/images`, keine API-Aenderung). Gespeichert wird vorerst im
+ * localStorage des Browsers, Schluessel je Benutzerkennung; ein Datenbankfeld
+ * kann folgen, wenn die Funktion bleibt.
+ */
+
+export type BackgroundPresetId = 'mist' | 'sage' | 'bloom' | 'dunes' | 'mosaic';
+
+export type DashboardBackground =
+  | { kind: 'none' }
+  | { kind: 'preset'; id: BackgroundPresetId }
+  | { kind: 'image'; imageId: string };
+
+export const NO_BACKGROUND: DashboardBackground = { kind: 'none' };
+
+function svgUrl(svg: string): string {
+  return `url("data:image/svg+xml,${encodeURIComponent(svg)}")`;
+}
+
+const VIEW = 'xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1600 1000" preserveAspectRatio="xMidYMid slice"';
+
+function bloom(base: string, a: string, b: string, c: string): string {
+  return svgUrl(
+    `<svg ${VIEW}><defs><filter id="f" x="-50%" y="-50%" width="200%" height="200%"><feGaussianBlur stdDeviation="90"/></filter></defs>` +
+      `<rect width="1600" height="1000" fill="${base}"/>` +
+      `<g filter="url(#f)"><ellipse cx="1180" cy="240" rx="520" ry="360" fill="${a}"/>` +
+      `<ellipse cx="300" cy="820" rx="600" ry="340" fill="${b}"/>` +
+      `<ellipse cx="920" cy="930" rx="380" ry="240" fill="${c}"/></g>` +
+      // Feines Korn gegen Farbstufen im weichgezeichneten Verlauf.
+      `<filter id="n"><feTurbulence type="fractalNoise" baseFrequency="0.85" numOctaves="2" stitchTiles="stitch"/><feColorMatrix type="saturate" values="0"/></filter>` +
+      `<rect width="1600" height="1000" filter="url(#n)" opacity="0.06"/></svg>`,
+  );
+}
+
+function dunes(base: string, a: string, b: string, c: string): string {
+  return svgUrl(
+    `<svg ${VIEW}><rect width="1600" height="1000" fill="${base}"/>` +
+      `<path d="M0 600 C300 520 620 690 920 630 S1400 500 1600 580 L1600 1000 L0 1000Z" fill="${a}"/>` +
+      `<path d="M0 750 C360 680 660 820 1010 755 S1450 670 1600 730 L1600 1000 L0 1000Z" fill="${b}"/>` +
+      `<path d="M0 885 C400 835 800 930 1200 875 S1500 845 1600 865 L1600 1000 L0 1000Z" fill="${c}"/></svg>`,
+  );
+}
+
+function mosaic(base: string, alpha: number, yellowAlpha: number): string {
+  const tiles: [number, number, string, number?][] = [
+    [1060, 120, '#2a8f8f'],
+    [1260, 120, '#7a5cc2'],
+    [1260, 320, '#3a78c9'],
+    [1060, 320, '#b37a1f'],
+    [1460, 320, '#c65436'],
+    [860, 520, '#3f8f5a'],
+    [1260, 520, '#3a78c9'],
+    [1460, 720, '#7a5cc2'],
+    [1060, 720, '#2a8f8f'],
+    [140, 760, '#c65436'],
+  ];
+  const rects = tiles
+    .map(
+      ([x, y, fill]) =>
+        `<rect x="${x}" y="${y}" width="170" height="170" rx="34" fill="${fill}" fill-opacity="${alpha}"/>`,
+    )
+    .join('');
+  return svgUrl(
+    `<svg ${VIEW}><rect width="1600" height="1000" fill="${base}"/>${rects}` +
+      `<rect x="1060" y="520" width="170" height="170" rx="34" fill="#ffed00" fill-opacity="${yellowAlpha}" transform="rotate(12 1145 605)"/></svg>`,
+  );
+}
+
+export interface BackgroundPreset {
+  id: BackgroundPresetId;
+  /** Uebersetzungsschluessel unter `dashboard.background.presets`. */
+  labelKey: string;
+  light: string;
+  dark: string;
+}
+
+export const BACKGROUND_PRESETS: BackgroundPreset[] = [
+  { id: 'mist', labelKey: 'mist', light: '#e4e9f1', dark: '#1d2330' },
+  { id: 'sage', labelKey: 'sage', light: '#e3ebe6', dark: '#1c2521' },
+  {
+    id: 'bloom',
+    labelKey: 'bloom',
+    light: bloom('#e8ecf3', '#b7c7e6', '#bcdcd7', '#d4cbe9'),
+    dark: bloom('#1b1f28', '#2a3a58', '#21403c', '#352e4d'),
+  },
+  {
+    id: 'dunes',
+    labelKey: 'dunes',
+    light: dunes('#e6ebef', '#d3dde3', '#c1cfd8', '#aebfca'),
+    dark: dunes('#1a1f25', '#212930', '#28323a', '#303c45'),
+  },
+  {
+    id: 'mosaic',
+    labelKey: 'mosaic',
+    light: mosaic('#eceff3', 0.16, 0.35),
+    dark: mosaic('#1b1f26', 0.24, 0.3),
+  },
+];
+
+export function presetBackground(id: BackgroundPresetId, dark: boolean): string | null {
+  const preset = BACKGROUND_PRESETS.find((p) => p.id === id);
+  if (!preset) return null;
+  return dark ? preset.dark : preset.light;
+}
+
+function storageKey(userId: string): string {
+  return `tessera.dashboardBackground.${userId}`;
+}
+
+function isValid(value: unknown): value is DashboardBackground {
+  if (typeof value !== 'object' || value === null) return false;
+  const v = value as Record<string, unknown>;
+  if (v.kind === 'none') return true;
+  if (v.kind === 'preset') return BACKGROUND_PRESETS.some((p) => p.id === v.id);
+  if (v.kind === 'image') return typeof v.imageId === 'string' && v.imageId !== '';
+  return false;
+}
+
+/** Liest die Wahl; jeder Fehler (privates Fenster, kaputter Wert) ergibt „kein Hintergrund“. */
+export function loadDashboardBackground(userId: string): DashboardBackground {
+  try {
+    const raw = window.localStorage.getItem(storageKey(userId));
+    if (!raw) return NO_BACKGROUND;
+    const parsed: unknown = JSON.parse(raw);
+    return isValid(parsed) ? parsed : NO_BACKGROUND;
+  } catch {
+    return NO_BACKGROUND;
+  }
+}
+
+export function saveDashboardBackground(userId: string, value: DashboardBackground): void {
+  try {
+    window.localStorage.setItem(storageKey(userId), JSON.stringify(value));
+  } catch {
+    // Speicher gesperrt — die Wahl gilt dann nur fuer diese Sitzung.
+  }
+}