The entrypoint was calling init_auth_db.py → init_db() + seed_permissions()
before the FastAPI startup_event (where run_alembic_migrations() lived).
Since the _ensure_*() safety net was removed, seed_permissions() failed
with 'column roles.is_admin does not exist' on databases with old schema.
Now alembic upgrade head runs directly in the entrypoint, ensuring all
migrations are applied before any DB queries.