feat: initial commit - Habo habit tracking app

- Complete MVP with Repository Pattern, SQLite storage
- Provider + ChangeNotifier state management
- Navigation 2.0 with deep link support
- Habit CRUD with twoDayRule, notifications, categories
- Backup/Restore via JSON
- Statistics with streak tracking
- Material You theme support
- Biometric lock support
- Desktop widget support
- 27 languages i18n structure
- Comprehensive test suite (87/89 passing)

lib/repositories/backup_repository.dart

@@ -0,0 +1,11 @@
+abstract class BackupRepository {
+  Future<Map<String, dynamic>> exportAllData();
+  Future<void> importData(Map<String, dynamic> data);
+  Future<int> getDatabaseVersion();
+  Future<String> getDatabasePath();
+  Future<void> closeDatabase();
+  Future<void> reopenDatabase();
+  Future<int> getHabitCount();
+  Future<int> getEventCount();
+  Future<bool> validateDatabaseIntegrity();
+}