refactor: app metadata (#28113)

* refactor: app metadata

* refactor to per row store

* cleanup

* more test

* review changes

* more refactor

* refactor

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>

mobile/lib/infrastructure/entities/metadata.entity.dart

@@ -0,0 +1,18 @@
+import 'package:drift/drift.dart';
+import 'package:immich_mobile/infrastructure/utils/drift_default.mixin.dart';
+
+class MetadataEntity extends Table with DriftDefaultsMixin {
+  const MetadataEntity();
+
+  TextColumn get key => text()();
+
+  TextColumn get value => text()();
+
+  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
+
+  @override
+  Set<Column> get primaryKey => {key};
+
+  @override
+  String get tableName => "metadata";
+}