feat: Add a proper file saver

lib/pages/image_viewer.dart

@@ -24,8 +24,8 @@ class ImageViewerController extends State<ImageViewer> {
     VRouter.of(context).to('/rooms');
   }
 
-  /// Open this file with a system call.
-  void openFileAction() => widget.event.openFile(context);
+  /// Save this file with a system call.
+  void saveFileAction() => widget.event.saveFile(context);
 
   /// Go back if user swiped it away
   void onInteractionEnds(ScaleEndDetails endDetails) {

lib/pages/views/image_viewer_view.dart

@@ -31,7 +31,7 @@ class ImageViewerView extends StatelessWidget {
           ),
           IconButton(
             icon: Icon(Icons.download_outlined),
-            onPressed: controller.openFileAction,
+            onPressed: controller.saveFileAction,
             color: Colors.white,
             tooltip: L10n.of(context).downloadFile,
           ),