The full backup carried identity/lnd_aezeed.enc but NOT the per-node
wallet secret that encrypts it (secrets/lnd-wallet-password), so a
restored node could never decrypt its Lightning seed. The secrets dir
now rides the backup (archive v3; the .bak itself is
passphrase-encrypted). Restore gains a staging-presence guard so
restoring an older archive without a secrets dir can no longer displace
and delete the node's live secrets — covered by two new tests.
Backups can now also be downloaded through the browser: a session-gated
GET /api/blob/backup/<id> endpoint (under the existing nginx /api/blob
prefix, so no fleet nginx changes) plus a Download button next to
Verify / USB / Restore / Delete in Settings → Backup & Restore.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
