[EPIC] Support metadata undelete for container hierarchies

### Describe the proposal

Child of #12187.

Linear tracking: [DAT-322](https://linear.app/datastrato/issue/DAT-322/support-metadata-undelete-for-container-hierarchies)

Support metadata-only undelete for schemas, catalogs, and metalakes. A container restore revives the exact recorded deletion tree in one relational transaction. An incomplete generation fails without partially restoring metadata.

The cascade-hardening lane can begin after #12188. Exact schema/catalog recovery composes the leaf semantics from #12189. Whole-metalake recovery is the join point and also waits for the standalone metalake-root semantics in #12191.

Individual implementation tickets carry the precise dependency edges.

### Task list

- [ ] **TBD** — Complete and verify existing container-delete cascades
- [ ] **TBD** — Implement exact schema-tree recovery
- [ ] **TBD** — Implement exact catalog-tree recovery
- [ ] **TBD** — Implement exact whole-metalake recovery
- [ ] **TBD** — Complete backend, REST, Java client, OpenAPI, rollback, and concurrency validation