Implement task list rendering in preview mode

- Enabled GitHub Flavored Markdown (GFM) in marked.js for task list support
- Added custom CSS styling for task lists:
  - Hide bullet points, show only checkboxes
  - Increased checkbox size to 20px for better visibility
  - Green accent color for checked items
  - Flexbox layout for proper multi-line text alignment
- Task lists render as read-only checkboxes in preview mode

src/components/NoteEditor.tsx

@@ -24,6 +24,12 @@ interface NoteEditorProps {
 
 const imageCache = new Map<string, string>();
 
+// Configure marked to support task lists
+marked.use({
+  gfm: true,
+  breaks: true,
+});
+
 
 export function NoteEditor({ note, onUpdateNote, onToggleFavorite, onUnsavedChanges, categories, isFocusMode, onToggleFocusMode, editorFont = 'Source Code Pro', editorFontSize = 14, previewFont = 'Merriweather', previewFontSize = 16, api }: NoteEditorProps) {
   const [localContent, setLocalContent] = useState('');