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/widgets/asset_grid/control_bottom_app_bar.dart

@@ -39,6 +39,7 @@ class ControlBottomAppBar extends HookConsumerWidget {
   final void Function()? onEditLocation;
   final void Function()? onRemoveFromAlbum;
   final void Function()? onToggleLocked;
+  final void Function()? onDownload;
 
   final bool enabled;
   final bool unfavorite;
@@ -56,6 +57,7 @@ class ControlBottomAppBar extends HookConsumerWidget {
     required this.onAddToAlbum,
     required this.onCreateNewAlbum,
     required this.onUpload,
+    this.onDownload,
     this.onStack,
     this.onEditTime,
     this.onEditLocation,
@@ -158,6 +160,15 @@ class ControlBottomAppBar extends HookConsumerWidget {
             label: (unfavorite ? "unfavorite" : "favorite").tr(),
             onPressed: enabled ? onFavorite : null,
           ),
+        if (hasRemote && onDownload != null)
+          ConstrainedBox(
+            constraints: const BoxConstraints(maxWidth: 90),
+            child: ControlBoxButton(
+              iconData: Icons.download,
+              label: "download".tr(),
+              onPressed: onDownload,
+            ),
+          ),
         if (hasLocal && hasRemote && onDelete != null && !isInLockedView)
           ConstrainedBox(
             constraints: const BoxConstraints(maxWidth: 90),