Apply different unarchive icon for iOS

lib/ui/gallery_app_bar_widget.dart

@@ -364,11 +364,13 @@ class _GalleryAppBarWidgetState extends State<GalleryAppBarWidget> {
         message: showArchive ? "archive" : "unarchive",
         child: IconButton(
           icon: Icon(
-            Platform.isAndroid
+            Platform.isIOS
                 ? (showArchive
                     ? Icons.archive_outlined
                     : Icons.unarchive_outlined)
-                : CupertinoIcons.archivebox,
+                : (showArchive
+                    ? CupertinoIcons.archivebox
+                    : CupertinoIcons.archivebox_fill),
           ),
           onPressed: () {
             _handleVisibilityChangeRequest(