style: apply ruff auto-fix

- Auto-formatted code with ruff format
- Applied ruff linting fixes with --fix

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

app/models.py

@@ -684,6 +684,8 @@ class SharedLink(Base):
 
     created_at = Column(DateTime(timezone=True), server_default=func.now())
     revoked_at = Column(DateTime(timezone=True), nullable=True)
+
+
 class UserNotificationTarget(Base):
     """Per-user notification target (email or webhook channel)."""