Change remaining database placeholders to %s for consistency

vidai/database.py

@@ -755,7 +755,7 @@ def get_user_by_id(user_id: int) -> Optional[Dict[str, Any]]:
     """Get user by ID."""
     conn = get_db_connection()
     cursor = conn.cursor()
-    cursor.execute('SELECT id, username, email, role, active, created_at, last_login, avatar FROM users WHERE id = ?',
+    cursor.execute('SELECT id, username, email, role, active, created_at, last_login, avatar FROM users WHERE id = %s',
                    (user_id,))
     row = cursor.fetchone()
     conn.close()