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/db/schema.ts

@@ -39,6 +39,9 @@ export const apps = sqliteTable("apps", {
   installCommand: text("install_command"),
   startCommand: text("start_command"),
   chatContext: text("chat_context", { mode: "json" }),
+  isFavorite: integer("is_favorite", { mode: "boolean" })
+    .notNull()
+    .default(sql`0`),
 });
 
 export const chats = sqliteTable("chats", {