feat(mobile): add bulk download functionality (#18878)

* feat(mobile): add bulk download functionality and update UI messages

- Added `downloadAll` method to `IDownloadRepository` and its implementation in `DownloadRepository` to handle multiple asset downloads.
- Implemented `downloadAllAsset` in `DownloadStateNotifier` to trigger bulk downloads.
- Updated `DownloadService` to create download tasks for all selected assets.
- Enhanced UI with new download success and failure messages in `en.json`.
- Added download button to `ControlBottomAppBar` and integrated download functionality in `MultiselectGrid`.

* translations use i18n method t()

* Update mobile/lib/services/download.service.dart

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

* fix(mobile): update download logic in DownloadService

- Changed the download method to utilize downloadAll for handling multiple tasks.
- Simplified remoteId check by removing unnecessary condition.

* sort i18n keys

* remove the download signature from interface and logic as we use the downloadAll now

---------

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

mobile/lib/interfaces/download.interface.dart

@@ -7,7 +7,8 @@ abstract interface class IDownloadRepository {
   void Function(TaskProgressUpdate)? onTaskProgress;
 
   Future<List<TaskRecord>> getLiveVideoTasks();
-  Future<bool> download(DownloadTask task);
+  Future<List<bool>> downloadAll(List<DownloadTask> tasks);
+
   Future<bool> cancel(String id);
   Future<void> deleteAllTrackingRecords();
   Future<void> deleteRecordsWithIds(List<String> id);