Add PD to Serenity backup automation scaffolding

docs/operations/BACKUP_POLICY.md

@@ -26,6 +26,16 @@ Back up at minimum:
 
 Recommended dump locations: `/mnt/tank/docker/backups/db-dumps/`
 
+Repo-side scaffolding now lives under `automation/`:
+
+- `automation/bin/pd_backup_postgres.sh`
+- `automation/bin/pd_backup_sync_to_serenity.sh`
+- `automation/bin/run_pd_backups.sh`
+
+These are staged helper scripts only until they are deployed with a real `.env`, SSH trust to Serenity, and a live scheduler on PD.
+
+Recommended live deployment model on PD: a plain **root cron** job invoking `/usr/bin/bash bin/run_pd_backups.sh` from `/mnt/docker-ssd/docker/compose/automation`.
+
 ## .env File Backup Options
 1. **Private Gitea repo** — short term, push all .env files to a private repo on your local Gitea
 2. **Encrypted restic** — include .env files in restic backup with encryption, push offsite (Backblaze B2)