fix: wrap slowapi handler in typed async function to satisfy mypy signature check

app/api/main.py

@@ -6,6 +6,11 @@ from slowapi.errors import RateLimitExceeded
 from app.api.limiter import limiter
 import os
 from prometheus_fastapi_instrumentator import Instrumentator
+from starlette.requests import Request
+from starlette.responses import Response
+
+async def _rate_limit_exceeded_handler(request: Request, exc: Exception) -> Response:
+    return await _slowapi_handler(request, exc)  # type: ignore[arg-type]
 
 app = FastAPI(
     title="AI Code Review Agent",