feat(mobile): hash assets in isolate (#18924)

mobile/lib/domain/utils/background_sync.dart

@@ -7,6 +7,7 @@ import 'package:worker_manager/worker_manager.dart';
 class BackgroundSyncManager {
   Cancelable<void>? _syncTask;
   Cancelable<void>? _deviceAlbumSyncTask;
+  Cancelable<void>? _hashTask;
 
   BackgroundSyncManager();
 
@@ -45,6 +46,20 @@ class BackgroundSyncManager {
     });
   }
 
+// No need to cancel the task, as it can also be run when the user logs out
+  Future<void> hashAssets() {
+    if (_hashTask != null) {
+      return _hashTask!.future;
+    }
+
+    _hashTask = runInIsolateGentle(
+      computation: (ref) => ref.read(hashServiceProvider).hashAssets(),
+    );
+    return _hashTask!.whenComplete(() {
+      _hashTask = null;
+    });
+  }
+
   Future<void> syncRemote() {
     if (_syncTask != null) {
       return _syncTask!.future;