implemented comprehensive accessibility (A11y) support across the app

lib/view/pages/talk/widgets/chat_textfield.dart

@@ -268,6 +268,7 @@ class _ChatTextfieldState extends State<ChatTextfield> {
               ),
             ),
             IconButton(
+              tooltip: 'Antwort verwerfen',
               onPressed: () {
                 chatBloc.setReferenceMessageId(null);
                 _setDraftReply(null);