fix: harden container startup and user admin migration

migrations/add_user_is_admin.py

@@ -0,0 +1,52 @@
+"""
+Migration script to add the is_admin flag expected by the current User model.
+"""
+import logging
+
+from sqlalchemy import inspect, text
+
+logger = logging.getLogger(__name__)
+
+
+def run_migration():
+    """
+    Add user.is_admin and backfill it from the existing admin role assignment.
+    Returns:
+    - True: if changes were made successfully
+    - None: if no changes were needed
+    - False: if errors occurred
+    """
+    from musicround import db
+
+    try:
+        inspector = inspect(db.engine)
+        existing_columns = [column["name"] for column in inspector.get_columns("user")]
+
+        if "is_admin" in existing_columns:
+            logger.info("is_admin column already exists")
+            return None
+
+        with db.engine.connect() as conn:
+            logger.info("Adding is_admin column")
+            conn.execute(text('ALTER TABLE "user" ADD COLUMN is_admin BOOLEAN DEFAULT 0'))
+            conn.execute(
+                text(
+                    """
+                    UPDATE "user"
+                       SET is_admin = 1
+                     WHERE id IN (
+                         SELECT ur.user_id
+                           FROM user_roles ur
+                           JOIN role r ON r.id = ur.role_id
+                          WHERE lower(r.name) = 'admin'
+                     )
+                    """
+                )
+            )
+            conn.commit()
+
+        logger.info("Added is_admin column")
+        return True
+    except Exception as e:
+        logger.error(f"Migration add_user_is_admin failed: {str(e)}")
+        return False