backup pipeline: configs, runbooks, NH3 Synology rest-server, cross-site rsync

Bundles the post-2026-04-21 work that built out the two-layer backup
architecture (PBS for VM images + restic for file/DB), plus the cross-
site mirror and the disaster-recovery runbook.

- configs/restic/esh-docker-vm/profiles.yaml: drop the obsolete
  *_offen_backup_data exclude (offen sidecars retired fleet-wide
  2026-04-23; restic now covers the equivalent scope directly).
- configs/restic/esh-vm-db/: new profile for the dedicated DB VM
  (10.0.50.60), with pre-backup pg_dumpall + mongodump hooks.
- configs/rsync/: ana-nas → nh3-nas (04:00 daily, runs as lkraven)
  and nh3-nas → ana-nas (05:00 daily, runs as root because DSM
  rest-server-nh3 writes mode-400 files only root can read).
- docs/runbooks/pbs-deployment.md: 9-phase PBS rollout runbook,
  refined during the 2026-04-22 deployment with per-hypervisor
  namespaces, NFSv3 + ZFS-case-insensitivity workaround, and the
  Synology syno_acl flatten step.
- docs/runbooks/disaster-recovery.md: blast-radius runbook ordered
  Tier 0 → 5 (ana-nas → hypervisors → Docker hosts → VMs → specialty);
  references incident memory + recovery-step playbooks per consumer.

configs/restic/esh-docker-vm/profiles.yaml

@@ -52,8 +52,8 @@ default:
       # Docker internals
       - /var/lib/docker/volumes/backingFsBlockDev
       - /var/lib/docker/volumes/metadata.db
-      # Offen sidecar's buffer / tmp (if any left behind)
-      - /var/lib/docker/volumes/*_offen_backup_data
+      # Offen `*_offen_backup_data` exclude removed 2026-04-23 — offen
+      # sidecars retired fleet-wide; no more offen-scratch volumes exist.
       # Ephemeral / regenerable
       - /opt/docker/compose/*/logs
       - "**/*.log"