Add scheduler improvements, API endpoints, and month calendar view

Backend:
- Add /api/customers/ endpoint (CustomerViewSet, CustomerSerializer)
- Add /api/services/ endpoint with Service model and migrations
- Add Resource.type field (STAFF, ROOM, EQUIPMENT) with migration
- Fix EventSerializer to return resource_id, customer_id, service_id
- Add date range filtering to EventViewSet (start_date, end_date params)
- Add create_demo_appointments management command
- Set default brand colors in business API

Frontend:
- Add calendar grid view for month mode in OwnerScheduler
- Fix sidebar navigation active link contrast (bg-white/10)
- Add default primaryColor/secondaryColor fallbacks in useBusiness
- Disable WebSocket (backend not implemented) to stop reconnect loop
- Fix Resource.type.toLowerCase() error by adding type to backend

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/hooks/useAppointmentWebSocket.ts

@@ -35,6 +35,9 @@ interface UseAppointmentWebSocketOptions {
   onError?: (error: Event) => void;
 }
 
+// WebSocket is not yet implemented in the backend - disable for now
+const WEBSOCKET_ENABLED = false;
+
 /**
  * Transform backend appointment format to frontend format
  */
@@ -60,6 +63,9 @@ function transformAppointment(data: WebSocketMessage['appointment']): Appointmen
  */
 export function useAppointmentWebSocket(options: UseAppointmentWebSocketOptions = {}) {
   const { enabled = true, onConnected, onDisconnected, onError } = options;
+
+  // Early return if WebSocket is globally disabled
+  const effectivelyEnabled = enabled && WEBSOCKET_ENABLED;
   const queryClient = useQueryClient();
   const wsRef = useRef<WebSocket | null>(null);
   const reconnectTimeoutRef = useRef<NodeJS.Timeout | null>(null);
@@ -138,7 +144,7 @@ export function useAppointmentWebSocket(options: UseAppointmentWebSocketOptions
   // Main effect to manage WebSocket connection
   // Only depends on `enabled` - other values are read from refs or called as functions
   useEffect(() => {
-    if (!enabled) {
+    if (!effectivelyEnabled) {
       return;
     }
 
@@ -285,7 +291,7 @@ export function useAppointmentWebSocket(options: UseAppointmentWebSocketOptions
 
       setIsConnected(false);
     };
-  }, [enabled]); // Only re-run when enabled changes
+  }, [effectivelyEnabled]); // Only re-run when enabled changes
 
   const reconnect = useCallback(() => {
     isCleaningUpRef.current = false;