fix: Use api_route for HEAD method support in assets proxy

services/city-service/routes_city.py

@@ -325,8 +325,7 @@ async def update_agent_visibility_endpoint(
 # Assets & Branding API (Task 042)
 # =============================================================================
 
-@router.get("/assets/proxy/{path:path}")
-@router.head("/assets/proxy/{path:path}")
+@router.api_route("/assets/proxy/{path:path}", methods=["GET", "HEAD"])
 async def proxy_asset(path: str, request: Request):
     """
     Proxy endpoint for serving MinIO assets.