优化代码，删除无用代码

lib/widgets/app_refresh_indicator.dart

@@ -1,29 +0,0 @@
-import 'package:flutter/material.dart';
-
-/// 自定义下拉刷新包装器 — 统一使用品牌色
-class AppRefreshIndicator extends StatelessWidget {
-  final Future<void> Function() onRefresh;
-  final Widget child;
-  final String? semanticsLabel;
-
-  const AppRefreshIndicator({
-    super.key,
-    required this.onRefresh,
-    required this.child,
-    this.semanticsLabel,
-  });
-
-  @override
-  Widget build(BuildContext context) {
-    final colors = Theme.of(context).colorScheme;
-    return RefreshIndicator(
-      onRefresh: onRefresh,
-      color: colors.primary,
-      backgroundColor: colors.surface,
-      strokeWidth: 2.5,
-      displacement: 60,
-      semanticsLabel: semanticsLabel,
-      child: child,
-    );
-  }
-}