feat: add visual todo list panel

- Add TodoPanel component to display TodoWrite tool calls
- Create todos Svelte store to track todo state
- Emit todo-update Tauri event when TodoWrite is called
- Add todo button to status bar (next to session history)
- Display todos with status icons, progress bar, and completion count
- Real-time updates as I work through tasks

Closes #132

package.json

@@ -64,6 +64,7 @@
     "@tauri-apps/plugin-store": "^2",
     "codemirror": "^6.0.2",
     "highlight.js": "^11.11.1",
+    "lucide-svelte": "^0.563.0",
     "marked": "^17.0.1"
   },
   "devDependencies": {