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/services/download.service.dart

@@ -159,9 +159,19 @@ class DownloadService {
     return await FileDownloader().cancelTaskWithId(id);
   }
 
+  Future<List<bool>> downloadAll(List<Asset> assets) async {
+    return await _downloadRepository
+        .downloadAll(assets.expand(_createDownloadTasks).toList());
+  }
+
   Future<void> download(Asset asset) async {
+    final tasks = _createDownloadTasks(asset);
+    await _downloadRepository.downloadAll(tasks);
+  }
+
+  List<DownloadTask> _createDownloadTasks(Asset asset) {
     if (asset.isImage && asset.livePhotoVideoId != null && Platform.isIOS) {
-      await _downloadRepository.download(
+      return [
         _buildDownloadTask(
           asset.remoteId!,
           asset.fileName,
@@ -171,9 +181,6 @@ class DownloadService {
             id: asset.remoteId!,
           ).toJson(),
         ),
-      );
-
-      await _downloadRepository.download(
         _buildDownloadTask(
           asset.livePhotoVideoId!,
           asset.fileName
@@ -185,16 +192,20 @@ class DownloadService {
             id: asset.remoteId!,
           ).toJson(),
         ),
-      );
-    } else {
-      await _downloadRepository.download(
-        _buildDownloadTask(
-          asset.remoteId!,
-          asset.fileName,
-          group: asset.isImage ? downloadGroupImage : downloadGroupVideo,
-        ),
-      );
+      ];
     }
+
+    if (asset.remoteId == null) {
+      return [];
+    }
+
+    return [
+      _buildDownloadTask(
+        asset.remoteId!,
+        asset.fileName,
+        group: asset.isImage ? downloadGroupImage : downloadGroupVideo,
+      ),
+    ];
   }
 
   DownloadTask _buildDownloadTask(