fix part 3

backend/app/api/sharing.py

@@ -1,6 +1,6 @@
 """Board sharing API endpoints."""
 
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, HTTPException, status
@@ -54,7 +54,7 @@ def validate_share_link(token: str, db: Session, required_permission: str = "vie
         )
 
     # Check expiration
-    if share_link.expires_at and share_link.expires_at < datetime.now(timezone.utc):
+    if share_link.expires_at and share_link.expires_at < datetime.now(UTC):
         raise HTTPException(
             status_code=status.HTTP_403_FORBIDDEN,
             detail="Share link has expired",
@@ -69,7 +69,7 @@ def validate_share_link(token: str, db: Session, required_permission: str = "vie
 
     # Update access tracking
     share_link.access_count += 1
-    share_link.last_accessed_at = datetime.now(timezone.utc)
+    share_link.last_accessed_at = datetime.now(UTC)
     db.commit()
 
     return share_link