hub-db-backup.sh v1.2 - verified daily backup of the llmmsg-srv hub DB

BACKS UP /var/lib/llmmsg-srv/v2.sqlite - the same file llmmsg-kpi-report.sh reads, i.e. the fleet's whole message history. WAL-safe + row-count verified (never cp). Runs 07:45 UTC daily via hub-db-backup.timer; a healthy run is SILENT, so absence of a message is not evidence it ran. Registry rows 165 (script, bin-venus-cc) + 166 (scheduled job, nw-venus-cc). Elazar GO 2026-08-22 option (b): BACKUP NOW, RESTORE DRILL LATER - the restore drill is still owed and is NOT covered by this item.