fix: added delete function

lib/services/data_transfer_service.dart

@@ -20,6 +20,7 @@ class DataTransferService {
   static Future<void> deleteAllData(BuildContext context) async {
     final db = Provider.of<AppDatabase>(context, listen: false);
 
+    await db.statisticDao.deleteAllStatistics();
     await db.matchDao.deleteAllMatches();
     await db.teamDao.deleteAllTeams();
     await db.groupDao.deleteAllGroups();