feat: add operations health and domain setup polish

backend/app/models/dns_cache.py

@@ -1,4 +1,4 @@
-from datetime import UTC, datetime
+from datetime import datetime, timezone
 
 from sqlalchemy import Boolean, Column, DateTime, Index, Integer, String, Text, UniqueConstraint
 
@@ -6,7 +6,7 @@ from app.core.database import Base
 
 
 def _utcnow_naive() -> datetime:
-    return datetime.now(UTC).replace(tzinfo=None)
+    return datetime.now(timezone.utc).replace(tzinfo=None)
 
 
 class DNSCache(Base):