Summary

• add deterministic rc admin bucket-metadata export archives with atomic mode-0600 file replacement and bounded multi-bucket selection
• add import from protected files or stdin with explicit fail, overwrite, or skip conflict handling and mutation-free dry-run
• use typed bounded Admin API transport with archive entry, decompression, and total-size limits
• fail closed when exported replication targets contain redacted credentials that cannot be safely restored
• preserve per-bucket partial outcomes, cancellation semantics, and secret-free output

BREAKING contract update

The protected command reference is extended with bucket metadata export/import and its explicit conflict and secret-handling contract. Existing commands remain backward compatible.

Validation

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• git diff --check

Closes rustfs/backlog#1494
Refs rustfs/backlog#1380