Added `get_user_by_id_regardless_active` in user repository to support activation/deactivation workflows, updated `user_service` to use it, and refactored `_enrich_release_config` in `app_dsl_service` to accept `default_model_config_id` as a parameter instead of reading from config dict.
- Remove unique=True from username column in User model
- Remove username duplicate check in create_user and create_superuser
- Add migration to drop unique index on username, keep email unique
