* feat(kms): add backup and restore admin API
Wires the merged KMS backup contract, Local export and Local restore into
the admin API: export a sealed bundle, run a zero-write restore preflight,
execute a confirmed restore, roll an interrupted restore back, and report
subsystem readiness.
- Dedicated kms:Backup / kms:Restore actions, recorded in the admin route
matrix. Neither is reachable through any other KMS action.
- Restore requires two independent confirmations: an echo of the bundle
manifest's backup id, and an explicitly named conflict policy (the
default never writes).
- The backup KEK comes from the environment and is refused when it reuses
a secret of the configured backend, compared both as the literal value
and as raw key bytes.
- No endpoint accepts a path: bundles are addressed by a validated name
under a configured root, and the restore target is always the server's
own configured key directory.
- Bundles now carry a sanitized configuration artifact built as an
allowlist projection, so a future backend credential field cannot leak
into a bundle by default. Restore verifies it and never applies it.
- Audit entries go through the existing KMS admin wiring and carry
identifiers only.
* test(kms): pin the backup admin API gates
Fixes the test KEK to a real 32-byte value and drives the export refusal
from the configured backend rather than from the handle that happens to
be available, so a Local handle cannot export on behalf of a backend
whose material RustFS does not own.
