feature(mobile): Hardening synchronization mechanism + Pull to refresh (#2085)

* fix(mobile): allow syncing duplicate local IDs

* enable to run isar unit tests on CI

* serialize sync operations, add pull to refresh on timeline

---------

Co-authored-by: Fynn Petersen-Frey <zoodyy@users.noreply.github.com>

mobile/test/async_mutex_test.dart

@@ -0,0 +1,41 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/utils/async_mutex.dart';
+
+void main() {
+  group('Test AsyncMutex grouped', () {
+    test('test ordered execution', () async {
+      AsyncMutex lock = AsyncMutex();
+      List<int> events = [];
+      expect(0, lock.enqueued);
+      lock.run(
+        () => Future.delayed(
+          const Duration(milliseconds: 10),
+          () => events.add(1),
+        ),
+      );
+      expect(1, lock.enqueued);
+      lock.run(
+        () => Future.delayed(
+          const Duration(milliseconds: 3),
+          () => events.add(2),
+        ),
+      );
+      expect(2, lock.enqueued);
+      lock.run(
+        () => Future.delayed(
+          const Duration(milliseconds: 1),
+          () => events.add(3),
+        ),
+      );
+      expect(3, lock.enqueued);
+      await lock.run(
+        () => Future.delayed(
+          const Duration(milliseconds: 10),
+          () => events.add(4),
+        ),
+      );
+      expect(0, lock.enqueued);
+      expect(events, [1, 2, 3, 4]);
+    });
+  });
+}