fix(web): Notiz-Widget folgt dem Hell/Dunkel-Schalter von Tessera statt der Systemeinstellung

- useTheme (next-themes) + mounted-Guard wie changelog-view.tsx
- data-color-mode am Wurzel-Div folgt resolvedTheme statt fest 'auto'
- zwei neue Tests (dark/light) via vi.hoisted-Themenzustand

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/web/src/components/dashboard/widgets/note-widget.tsx

@@ -2,6 +2,7 @@
 
 import { useCallback, useEffect, useRef, useState } from 'react';
 import { useTranslations } from 'next-intl';
+import { useTheme } from 'next-themes';
 import MDEditor, { commands } from '@uiw/react-md-editor';
 import rehypeSanitize from 'rehype-sanitize';
 import type { WidgetProps } from '../widget-registry';
@@ -41,6 +42,17 @@ const NOTE_COMMANDS = [
 
 export function NoteWidget({ instanceId, config }: WidgetProps) {
   const t = useTranslations('widgets');
+  const { resolvedTheme } = useTheme();
+  const [mounted, setMounted] = useState(false);
+
+  useEffect(() => {
+    setMounted(true);
+  }, []);
+
+  // quick-260916-j4f: folgt dem Tessera-Schalter statt der
+  // Betriebssystem-Einstellung, Muster changelog-view.tsx.
+  const colorMode: 'light' | 'dark' = mounted && resolvedTheme === 'dark' ? 'dark' : 'light';
+
   const [title, setTitle] = useState<string>(
     (config.title as string) || t('note.defaultTitle'),
   );
@@ -128,7 +140,7 @@ export function NoteWidget({ instanceId, config }: WidgetProps) {
   );
 
   return (
-    <div className="flex h-full flex-col overflow-hidden" data-color-mode="auto">
+    <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">
         <input