This PR implements favorite apps feature and addresses issue #827 
    
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## 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).

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