feat: add category renaming functionality (v0.1.5)

- Add double-click to rename categories (deprecated in favor of pencil icon)
- Add pencil icon on hover for intuitive category renaming
- Click pencil icon to enter inline rename mode
- Show helpful hint (Enter to save, Esc to cancel)
- Update all notes with old category name to new name
- Sync category changes to server
- Update selected category if currently viewing renamed category
- Bump version to 0.1.5

package.json

@@ -1,7 +1,7 @@
 {
   "name": "nextcloud-notes-tauri",
   "private": true,
-  "version": "0.1.4",
+  "version": "0.1.5",
   "type": "module",
   "scripts": {
     "dev": "vite",