feat: daily encrypted database backup to a bucket of its own

A backup service runs pg_dump every day at 03:00 Brasília, checks the archive,
encrypts it with age to a public key and uploads it with a token for that
bucket only. The server cannot read or delete backups: the private key stays
with the owner, the bucket's lifecycle rule expires copies and its lock stops
early deletion. Each run is recorded and shown on the Kanban's Integrations
tab. tests/backup_test.py backs up, restores into a scratch database and
compares the rows in CI. Setup and restore: docs/BACKUP.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -864,6 +864,12 @@ print-file evidence still need correction before this item can close.
 - `[ ]` 5.13 — Define production recovery: scheduled encrypted offsite database
   and object backups, a consistent snapshot boundary, Swarm data placement and
   a restore rehearsal that opens every required live order file.
+  **2026-09-29:** database part built. The `backup` service dumps daily,
+  encrypts with age (the server holds only the public key) and uploads to a
+  bucket of its own, whose lifecycle rule expires copies and whose lock keeps
+  them from being deleted early. The Kanban shows the latest run, and
+  `tests/backup_test.py` restores a copy in CI. Setup and restore:
+  docs/BACKUP.md. Artwork is not copied: it is temporary and already on R2.
 - `[ ]` 5.14 — Promote and verify one immutable release. **2026-09-24:** green
   pushes to `main` now publish images and Portainer's pull-and-redeploy is the
   release gate; the source preflight is advisory unless enforced by variable,