fix: Handle asyncio.CancelledError

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

app.py

@@ -2698,8 +2698,9 @@ except Exception as e:
                 f"Base directory: {BASE_DIR}"
             )
         except asyncio.CancelledError:
-            logger.info("[API_CANCEL] Error fallback / was cancelled")
-            raise
+            logger.debug("[API_CANCEL] Error fallback / was cancelled")
+            from fastapi.responses import Response
+            return Response(status_code=204, content=None)
 
     @fallback_app.get("/api/health")
     async def error_health():
@@ -2711,8 +2712,9 @@ except Exception as e:
                 "error_log": str(ERROR_LOG_FILE)
             }
         except asyncio.CancelledError:
-            logger.info("[API_CANCEL] Error fallback /api/health was cancelled")
-            raise
+            logger.debug("[API_CANCEL] Error fallback /api/health was cancelled")
+            from fastapi.responses import Response
+            return Response(status_code=204, content=None)
 
     # Add shutdown handler to fallback app too
     @fallback_app.on_event("shutdown")