feat(dashboard): auf jedem Bildschirm dasselbe Bild – Leinwand je Reiter, massstaeblich skaliert

Je Reiter wird die Flaeche des ersten Desktop-Bildschirms als __canvas im
Layout-JSON gespeichert (ohne API/DB-Aenderung, GRID_VERSION bleibt 3).
Das Raster rendert in Leinwandbreite und wird per transform: scale(min(bw/cw, bh/ch))
eingepasst, Schrift eingeschlossen, ohne Scrollen; unter 768 px wie bisher.
Ziehen/Groesse aendern unter Skalierung ueber eine eigene Positionsstrategie
(createScaledStrategy aus react-grid-layout 2.2.3 rechnet den Rasterversatz falsch).
Im Browser nachgewiesen: 1920x1080 -> 1366x768 (Faktor 0,66), Ziehen +200 px
folgt der Maus, 700 px ohne Skalierung.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/app/(portal)/page.tsx

@@ -1,28 +1,32 @@
 'use client';
 
+import { useTranslations } from 'next-intl';
 import { useCallback, useEffect, useState } from 'react';
 import { createPortal } from 'react-dom';
-import { useTranslations } from 'next-intl';
-import { HEADER_ACTIONS_SLOT_ID } from '@/components/layout/header-slot';
+import {
+  BackgroundPicker,
+  DashboardBackdrop,
+  useDashboardBackground,
+} from '@/components/dashboard/dashboard-background';
 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 { WidgetCatalogModal } from '@/components/dashboard/widget-catalog-modal';
+import type { WidgetType } from '@/components/dashboard/widget-registry';
 import { registerWidget } from '@/components/dashboard/widget-registry';
-import { ClockWidget } from '@/components/dashboard/widgets/clock-widget';
-import { SearchWidget } from '@/components/dashboard/widgets/search-widget';
-import { CalendarWidget } from '@/components/dashboard/widgets/calendar-widget';
-import { NoteWidget } from '@/components/dashboard/widgets/note-widget';
 import { CalculatorWidget } from '@/components/dashboard/widgets/calculator-widget';
-import { StopwatchWidget } from '@/components/dashboard/widgets/stopwatch-widget';
+import { CalendarWidget } from '@/components/dashboard/widgets/calendar-widget';
+import { ClockWidget } from '@/components/dashboard/widgets/clock-widget';
 import { FavoritesWidget } from '@/components/dashboard/widgets/favorites-widget';
+import { NoteWidget } from '@/components/dashboard/widgets/note-widget';
 import { PictureFrameWidget } from '@/components/dashboard/widgets/picture-frame-widget';
-import { XframeWidget } from '@/components/dashboard/widgets/xframe-widget';
 import { ProxmoxWidget } from '@/components/dashboard/widgets/proxmox-widget';
 import { ReminderWidget } from '@/components/dashboard/widgets/reminder-widget';
+import { SearchWidget } from '@/components/dashboard/widgets/search-widget';
+import { StopwatchWidget } from '@/components/dashboard/widgets/stopwatch-widget';
+import { XframeWidget } from '@/components/dashboard/widgets/xframe-widget';
+import { HEADER_ACTIONS_SLOT_ID } from '@/components/layout/header-slot';
 import { useDashboardStore } from '@/lib/stores/dashboard-store';
-import type { WidgetType } from '@/components/dashboard/widget-registry';
 
 const API_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001';
 
@@ -71,6 +75,7 @@ export default function DashboardPage() {
     activeDashboardId,
     isSwitchingDashboard,
     layouts,
+    canvas,
     widgets,
     isEditMode,
     isLoading,
@@ -85,6 +90,7 @@ export default function DashboardPage() {
     renameDashboard,
     deleteDashboard,
     reorderDashboards,
+    captureCanvas,
   } = useDashboardStore();
 
   // Load dashboard data on mount
@@ -200,6 +206,8 @@ export default function DashboardPage() {
           onRemoveWidget={removeWidget}
           onOpenCatalog={() => setCatalogOpen(true)}
           onQuickAdd={(type) => addWidget(type)}
+          canvas={canvas}
+          onCaptureCanvas={captureCanvas}
         />
       )}