feat: Add WYSIWYG event editor with date/time picker

Major features:
- True WYSIWYG editor using CodeMirror 6 with inline formatting
  - Bold, italic, strikethrough render inline (syntax hidden until cursor on line)
  - Interactive checkboxes for task lists (click to toggle)
  - Fenced code block highlighting with background styling
  - Links show as clickable text, URL hidden until editing
- Full undo/redo support (Ctrl+Z, Ctrl+Shift+Z)
- Editable event titles directly in the modal
- Date/time picker with:
  - Combined datetime-local inputs for From/To
  - Smart time display (only shows time when not midnight)
  - Live summary preview of formatted date range
- Settings toggle between WYSIWYG and plain text editor modes
- Fixed title parsing bug with times containing colons (e.g., 10:30am)
- Cleaner date format when dragging events on timeline

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cybersader

package-lock.json

@@ -34,6 +34,9 @@
 		"watch": "^0.13.0"
 	},
 	"dependencies": {
+		"@codemirror/commands": "^6.10.0",
+		"@codemirror/lang-markdown": "^6.5.0",
+		"@codemirror/language": "^6.11.3",
 		"@codemirror/state": "^6.4.1",
 		"@codemirror/view": "^6.26.3",
 		"@markwhen/calendar": "^1.3.4",