refactor: 重构前端 UI 组件与后端 AgentScope schemas

apps/lib/features/todo/ui/screens/todo_detail_screen.dart

@@ -3,6 +3,7 @@ import 'package:go_router/go_router.dart';
 import 'package:lucide_icons/lucide_icons.dart';
 import '../../../../core/di/injection.dart';
 import '../../../../core/theme/design_tokens.dart';
+import '../../../../shared/widgets/page_header.dart' as widgets;
 import '../../../../shared/widgets/app_button.dart';
 import '../../../../shared/widgets/toast/toast.dart';
 import '../../../../shared/widgets/toast/toast_type.dart';
@@ -101,26 +102,7 @@ class _TodoDetailScreenState extends State<TodoDetailScreen> {
         padding: const EdgeInsets.only(left: 16, right: 16, top: 12, bottom: 8),
         child: Row(
           children: [
-            GestureDetector(
-              onTap: () => Navigator.of(context).pop(),
-              child: Container(
-                width: 36,
-                height: 36,
-                decoration: BoxDecoration(
-                  color: AppColors.messageBtnWrap,
-                  borderRadius: BorderRadius.circular(18),
-                  border: Border.all(
-                    color: AppColors.messageBtnBorder,
-                    width: 1,
-                  ),
-                ),
-                child: const Icon(
-                  LucideIcons.chevronLeft,
-                  size: 16,
-                  color: AppColors.slate700,
-                ),
-              ),
-            ),
+            widgets.BackButton(onPressed: () => Navigator.of(context).pop()),
             const Spacer(),
             if (_todo != null) ...[
               IconButton(