Add pgBackRest-based PITR for the production database, shipped disarmed
(archive_mode and the base-backup timer gated off) so it stays inert until the
operator arms it before real payments — an un-armed deploy cannot pile WAL onto
the disk.
- Postgres now builds from a thin image carrying pgBackRest (archive_command runs
in-process); the prod overlay wires an encrypted (AES-256-CBC), path-style S3
repository with 30-day retention and a daily full base-backup systemd timer.
- Repository config/secrets flow through the PROD_PGBACKREST_* Gitea set and
write-prod-env.sh; prod-rollback re-renders the same env so a rollback cannot
disarm archiving.
- Grafana alerts watch pg_stat_archiver (failing / stalled), absent-safe on the
test contour, which never archives.
- Fix the pre-migration pg_dump to snapshot the whole database (was backend-only,
silently excluding payments).
- Document the PITR runbook, the arming sequence and the restore drill in
deploy/README.md; record the measured cost/perf assessment.
Ilia Denisov