implemented comprehensive accessibility (A11y) support across the app

lib/view/pages/share_intent/share_chat_picker.dart

@@ -76,6 +76,7 @@ class ShareChatPicker extends StatelessWidget {
         actions: [
           Builder(
             builder: (ctx) => IconButton(
+              tooltip: 'Suchen',
               icon: const Icon(Icons.search),
               onPressed: () {
                 final rooms = ctx.read<ChatListBloc>().state.data?.rooms;