- Add accounts-only pg_dump (users + passkeys) to backup script for
lightweight disaster recovery when clients still have data
- Add pipefail to backup script to catch silent dump failures
- Add test endpoint to simulate partial server revert (ops-after/:serverSeq)
- Add 6 e2e tests covering all disaster recovery scenarios:
complete data loss, partial revert, accounts-only restore (API + SQL),
full dump restore + reset account, and all-clients-lost recovery
- Add backup-and-recovery.md with setup, recovery procedures, and
decision tree