implementing favorite apps feature (#1410)

This PR implements favorite apps feature and addresses issue #827 
    
<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Adds a favorite apps feature with a star toggle in the sidebar.
Favorites are grouped separately and persisted, with optimistic UI
updates and e2e tests.

- **New Features**
- Added isFavorite to the apps schema and an IPC handler
(add-to-favorite) to toggle and persist the state.
  - Updated AppList to show “Favorite apps” and “Other apps” sections.
- Introduced AppItem component with a star button; uses
useAddAppToFavorite for optimistic updates and toasts.
  - Added Playwright tests to verify favoriting and unfavoriting.

- **Migration**
- Run DB migrations to add the apps.is_favorite column (defaults to 0).

<!-- End of auto-generated description by cubic. -->

src/preload.ts

@@ -127,6 +127,8 @@ const validInvokeChannels = [
   "prompts:create",
   "prompts:update",
   "prompts:delete",
+  // adding app to favorite
+  "add-to-favorite",
   // Test-only channels
   // These should ALWAYS be guarded with IS_TEST_BUILD in the main process.
   // We can't detect with IS_TEST_BUILD in the preload script because