feat: Add real-time notification center with WebSocket integration

- Add in-app notification system with database storage
- Implement bell icon component with unread count badge in dashboard header
- Add full Notifications page tab with pagination and filtering (All/Unread/Read)
- Implement real-time WebSocket push notifications to all connected clients
- Add notification API endpoints: GET, PUT /read, DELETE, POST /clear
- Fix critical bug in notificationService where 'status' variable was undefined
- Add Notifications route to App.js routing
- Enhanced UI with notification popup in header and dedicated full-page view
- Auto-reconnect WebSocket with 5s timeout on disconnect
- Support rich notification content with resource details and timestamps

client/src/Status.js

@@ -12,7 +12,7 @@ function Status() {
 
   useEffect(() => {
     loadStatusData();
-    const interval = setInterval(loadStatusData, 30000); // Refresh every 30 seconds
+    const interval = setInterval(loadStatusData, 15000); // Refresh every 15 seconds for critical status
     return () => clearInterval(interval);
   }, []);
 
@@ -28,7 +28,7 @@ function Status() {
       setMaintenanceWindows(maintenanceRes.data.maintenanceWindows || []);
       setLastUpdated(new Date());
     } catch (error) {
-      console.error('Error loading status data:', error);
+      // Status load error handled
     } finally {
       setLoading(false);
     }