[Tracking] Database migration and observability cutover

[letwir]

Completion condition: Database_vmagent is writing new samples to the VictoriaMetrics instance on db.tigris-tailor.ts.net and the increase is verified.

Execution order:

1. [VictoriaMetrics] NAS-backed DB migration to LXC 240 #1 Finish and validate NAS-backed VictoriaMetrics migration.
2. [VictoriaMetrics] Rescue /var/lib/vm-rescue-forensic into LXC 240 #2 Rescue readable data from /var/lib/vm-rescue-forensic.
3. [VictoriaMetrics] Consolidate systemd storage paths on LXC 240 #3 Consolidate VictoriaMetrics storage paths and systemd service.
4. [VictoriaLogs] Install service and migrate Loki history #4 Install VictoriaLogs and migrate Loki history.
5. [Alloy] Redirect all SSH-reachable Alloy log outputs to VictoriaLogs #5 Redirect Alloy hosts to VictoriaLogs.
6. [FreshRSS] Migrate MariaDB data to existing PostgreSQL database #6 Migrate FreshRSS from MariaDB to PostgreSQL.
7. [Backup] Configure monthly last-Saturday DBMS backups #7 Configure monthly last-Saturday backups.
8. [vmagent] Cut over remote_write to new DB and verify live ingestion #8 Cut over vmagent and verify live ingestion.

The automation must progress to the next safe issue after each dependency completes. Keep source databases intact until validation succeeds.

[letwir]

Tracking started. Active work: #1. Final completion gate remains #8: Database_vmagent writes to the new DB and new samples/timestamps increase.