fix: use deleteSnapshotFromLocalDB in syncWithRemote

syncWithRemote was calling v.Repositories.Snapshots.Delete() directly,
which only removes the snapshots row. This leaves orphaned rows in
snapshot_files, snapshot_blobs, and uploads tables.

Replace with deleteSnapshotFromLocalDB() which properly cleans up all
related tables before deleting the snapshot record.

closes #10

internal/vaultik/snapshot.go

@@ -802,7 +802,7 @@ func (v *Vaultik) syncWithRemote() error {
 		snapshotIDStr := snapshot.ID.String()
 		if !remoteSnapshots[snapshotIDStr] {
 			log.Info("Removing local snapshot not found in remote", "snapshot_id", snapshot.ID)
-			if err := v.Repositories.Snapshots.Delete(v.ctx, snapshotIDStr); err != nil {
+			if err := v.deleteSnapshotFromLocalDB(snapshotIDStr); err != nil {
 				log.Error("Failed to delete local snapshot", "snapshot_id", snapshot.ID, "error", err)
 			} else {
 				removedCount++