fix part 3

backend/app/database/models/share_link.py

@@ -1,9 +1,8 @@
 """ShareLink model for board sharing functionality."""
 
 import uuid
-from datetime import datetime, timezone
 
-from sqlalchemy import Boolean, Column, DateTime, ForeignKey, Integer, String
+from sqlalchemy import Boolean, Column, DateTime, ForeignKey, Integer, String, func
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import relationship
 
@@ -19,7 +18,7 @@ class ShareLink(Base):
     board_id = Column(UUID(as_uuid=True), ForeignKey("boards.id", ondelete="CASCADE"), nullable=False)
     token = Column(String(64), unique=True, nullable=False, index=True)
     permission_level = Column(String(20), nullable=False)  # 'view-only' or 'view-comment'
-    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+    created_at = Column(DateTime, nullable=False, server_default=func.now())
     expires_at = Column(DateTime, nullable=True)
     last_accessed_at = Column(DateTime, nullable=True)
     access_count = Column(Integer, nullable=False, default=0)