refactor(mobile): DB repository for asset, backup, sync service (#12953)

* refactor(mobile): DB repository for asset, backup, sync service

* review feedback

* fix bug found by Alex

---------

Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/lib/repositories/database.repository.dart

@@ -0,0 +1,28 @@
+import 'dart:async';
+
+import 'package:immich_mobile/interfaces/database.interface.dart';
+import 'package:isar/isar.dart';
+
+/// copied from Isar; needed to check if an async transaction is already active
+const Symbol _zoneTxn = #zoneTxn;
+
+abstract class DatabaseRepository implements IDatabaseRepository {
+  final Isar db;
+  DatabaseRepository(this.db);
+
+  bool get inTxn => Zone.current[_zoneTxn] != null;
+
+  Future<T> txn<T>(Future<T> Function() callback) =>
+      inTxn ? callback() : transaction(callback);
+
+  @override
+  Future<T> transaction<T>(Future<T> Function() callback) =>
+      db.writeTxn(callback);
+}
+
+extension Asd<T> on QueryBuilder<T, dynamic, dynamic> {
+  QueryBuilder<T, T, O> noOp<O>() {
+    // ignore: invalid_use_of_protected_member
+    return QueryBuilder.apply(this, (query) => query);
+  }
+}