implemented comprehensive accessibility (A11y) support across the app

lib/view/pages/files/sharing/share_options_sheet.dart

@@ -239,6 +239,7 @@ class _ShareOptionsBodyState extends State<_ShareOptionsBody> {
               ),
               trailing: IconButton(
                 onPressed: () => copyToClipboard(context, _share.url!),
+                tooltip: 'Link kopieren',
                 icon: const Icon(Icons.copy_outlined),
               ),
             ),

lib/view/pages/files/sharing/sharee_picker_page.dart

@@ -127,6 +127,7 @@ class _ShareePickerPageState extends State<ShareePickerPage> {
                     ? null
                     : IconButton(
                         icon: const Icon(Icons.clear),
+                        tooltip: 'Leeren',
                         onPressed: () {
                           _searchController.clear();
                           _query = '';