chore(backup): ship takeone:backup command + nightly scheduler entry

Moves BackupCommand and config/backup.php from the pre-audit WIP that
got stashed on 2026-10-21 to master, and registers the command in the
Laravel scheduler so it runs at 03:30 Asia/Bahrain nightly.

The command handles sqlite (VACUUM INTO after a WAL checkpoint) and
mysql (mysqldump | gzip, verified with gzip -t) backends; verifies
every snapshot by re-opening it with PDO + PRAGMA integrity_check +
a sanity SELECT; ships an off-server copy via Storage::disk() when
BACKUP_DISK is set; and prunes artifacts older than BACKUP_RETAIN_DAYS
while always keeping at least BACKUP_KEEP_MINIMUM.

Scheduler entry mirrors the nas-auto-sync shape — withoutOverlapping
+ runInBackground so a slow upload doesn't block the next tick.

.env knobs:
  BACKUP_PATH          (default: data/backups)
  BACKUP_RETAIN_DAYS   (default: 14)
  BACKUP_KEEP_MINIMUM  (default: 3)
  BACKUP_DISK          (unset — warns on every run until configured)
  BACKUP_MEDIA_DEST    (unset — required when running with --media)
  BACKUP_MEDIA_DELETE  (default: false)

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

app/Console/Kernel.php

@@ -48,6 +48,14 @@ class Kernel extends ConsoleKernel
                  ->weeklyOn(1, '09:00')
                  ->withoutOverlapping()
                  ->runInBackground();
+
+        // Nightly database backup at 03:30 Asia/Bahrain. Writes to
+        // data/backups/db-YYYYMMDD-HHMMSS.sqlite, verifies the snapshot,
+        // and (when BACKUP_DISK is set) ships a copy off-server.
+        $schedule->command('takeone:backup')
+                 ->dailyAt('03:30')
+                 ->withoutOverlapping()
+                 ->runInBackground();
     }
 
     /**