Add debug logging to model_fallback callback in handlers.py

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/websocket/handlers.py

@@ -142,8 +142,11 @@ async def handle_analyze_message(
             if fallback_notified:
                 return
             fallback_notified = True
+            logger.info(f"[WEBSOCKET] Sending model_fallback notification to client: {client_id}")
             if manager.is_connected(client_id):
                 await manager.send_message(client_id, {"type": "model_fallback"})
+            else:
+                logger.warning(f"[WEBSOCKET] Cannot send model_fallback - client {client_id} not connected")
 
         # Run the analysis
         logger.info("[WEBSOCKET] Starting analysis...")