New DatabaseBackupHostedService + SqliteDatabaseBackupRunner:
- daily VACUUM INTO snapshot to <Data:Root>/backups (safe with WAL)
- catch-up backup at startup when none exists from the last 24h
- retention pruning (Backups:RetainCount, default 14)
- warns and stays idle on MySQL/MariaDB where external backups apply
Production previously had no automated database backup on Linux
(the /api/backup endpoint is Windows-DPAPI-only).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
cesnimda