key_backup_wire_schema_required· reason_code· applies to schema_validationStation device/key surface received a `ak.keys.backups.*` request body that does not validate as `ak.schema.key_backup.v1`. Wire backups MUST carry the dedicated key-backup envelope with `series_id` and `series_seq`; client-local secret-storage envelopes are not accepted on wire endpoints. See zh/crypto-media/device-lifecycle.md §11.