Add organization and task queue features

- Introduced new models for `Organization` and `ReviewTask` to manage organizations and review tasks.
- Implemented API endpoints for CRUD operations on organizations and tasks, including scanning organizations for repositories and PRs.
- Developed a background worker for sequential processing of review tasks with priority handling and automatic retries.
- Created frontend components for managing organizations and monitoring task queues, including real-time updates and filtering options.
- Added comprehensive documentation for organization features and quick start guides.
- Fixed UI issues and improved navigation for better user experience.

backend/app/main.py

@@ -45,9 +45,16 @@ async def lifespan(app: FastAPI):
     """Lifespan events"""
     # Startup
     await init_db()
+    
+    # Start task worker
+    from app.workers.task_worker import start_worker
+    await start_worker()
+    
     yield
+    
     # Shutdown
-    pass
+    from app.workers.task_worker import stop_worker
+    await stop_worker()
 
 
 # Create FastAPI app