further improved accessibility across the application and add tooltips to action buttons

lib/view/pages/files/widgets/files_sort_actions.dart

@@ -23,6 +23,8 @@ class FilesSortActions extends StatelessWidget {
       mainAxisSize: MainAxisSize.min,
       children: [
         PopupMenuButton<bool>(
+          tooltip:
+              'Sortierrichtung: ${ascending ? 'aufsteigend' : 'absteigend'}',
           icon: Icon(
             ascending ? Icons.text_rotate_up : Icons.text_rotation_down,
           ),
@@ -47,6 +49,8 @@ class FilesSortActions extends StatelessWidget {
           onSelected: onDirectionChanged,
         ),
         PopupMenuButton<SortOption>(
+          tooltip:
+              'Sortieren nach: ${SortOptions.getOption(currentSort).displayName}',
           icon: const Icon(Icons.sort),
           itemBuilder: (context) => SortOptions.options.keys
               .map(