vta-backup

The VTA's backup/restore subsystem, extracted from vta-service.

• ops — encrypted full-state export (every BACKED_UP keyspace, row for row; Argon2id KDF + AES-256-GCM), the import that stages a restore, the vta_did compatibility check, and the two-phase descriptor flow for the backup/* trust tasks.
• restore — applying a staged restore at boot, under the storage key the restored seed yields. A backup restores into a plain, hardened or TEE VTA from any of them.
• backup_bundle_store — the sealed backup-bundle store (bundle records + on-disk blobs).
• backup_bundle_sweeper — TTL sweep of expired backup bundles.

The operations take narrow dependencies (a BackupTarget — the store, its at-rest key and the kind of deployment — plus config) rather than a &AppState. Two vta-service-specific glue points are inverted and stay in vta-service:

• DescriptorDeps are borrowed from AppState there via a free constructor (operations::descriptor_deps_from_app_state).
• How a deployment adopts a restored seed is injected through the RestoreCommitter trait: SeedStoreCommitter here for plain and hardened VTAs, and vta-service's enclave committer, which seals the seed under KMS and reserves the anti-rollback counter.

Design: docs/05-design-notes/backup-restore-portability.md.

vta-service re-exports the crate as crate::operations::backup + crate::{backup_bundle_store,backup_bundle_sweeper}, so existing call sites are unchanged.

Part of the Verifiable Trust Infrastructure workspace. Apache-2.0.