feat: Tier2 backup pauses when destination drive is inactive (Inaktív)

Deactivated drives (Schedulable=false) now treated like disconnected for
Tier2 backups. New IsStoragePathSchedulable() checks active+connected+not
decommissioned. UI shows yellow "Cél meghajtó inaktív" badge, scheduler
skips silently with WARN log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/backup/crossdrive.go

@@ -104,6 +104,10 @@ func (r *CrossDriveRunner) RunAppBackup(ctx context.Context, stackName string) e
 		r.logger.Printf("[WARN] [backup] Cross-drive backup skipped for %s: destination not a registered storage (%s)", stackName, cfg.DestinationPath)
 		return nil
 	}
+	if !r.sett.IsStoragePathSchedulable(cfg.DestinationPath) {
+		r.logger.Printf("[WARN] [backup] Cross-drive backup skipped for %s: destination drive inactive (%s)", stackName, cfg.DestinationPath)
+		return nil
+	}
 
 	// Mark as running in settings
 	_ = r.sett.UpdateCrossDriveStatus(stackName, func(c *settings.CrossDriveBackup) {