feat(flutter): 增加目录加载诊断与前台重试

lib/core/widgets/catalog_debug_info.dart

@@ -0,0 +1,47 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+
+import '../config/app_config.dart';
+import '../theme/app_colors.dart';
+
+const TextStyle _debugStyle = TextStyle(
+  color: AppColors.subtle,
+  fontSize: 12,
+  height: 1.35,
+);
+
+/// 仅 debug 展示当前服务地址与目录请求的原始错误。
+class CatalogDebugInfo extends StatelessWidget {
+  const CatalogDebugInfo({super.key, required this.error});
+
+  final String? error;
+
+  @override
+  Widget build(BuildContext context) {
+    if (!kDebugMode) return const SizedBox.shrink();
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Text(
+          '服务地址：${AppConfig.apiBaseUrl}',
+          key: const Key('catalog-debug-endpoint'),
+          maxLines: 2,
+          overflow: TextOverflow.ellipsis,
+          textAlign: TextAlign.center,
+          style: _debugStyle,
+        ),
+        const SizedBox(height: 2),
+        Text(
+          '错误：${error ?? 'unknown'}',
+          key: const Key('catalog-debug-error'),
+          maxLines: 2,
+          overflow: TextOverflow.ellipsis,
+          textAlign: TextAlign.center,
+          style: _debugStyle,
+        ),
+      ],
+    );
+  }
+}

lib/core/widgets/empty_state.dart

@@ -25,6 +25,7 @@ class EmptyState extends StatelessWidget {
     this.actionLabel,
     this.actionKey,
     this.onAction,
+    this.footer,
     this.compact = false,
   });
 
@@ -34,6 +35,7 @@ class EmptyState extends StatelessWidget {
   final String? actionLabel;
   final Key? actionKey;
   final VoidCallback? onAction;
+  final Widget? footer;
   final bool compact;
 
   @override
@@ -65,6 +67,7 @@ class EmptyState extends StatelessWidget {
                   actionLabel: hasAction ? actionLabel : null,
                   actionKey: actionKey,
                   onAction: hasAction ? onAction : null,
+                  footer: footer,
                 ),
               ],
             ),
@@ -101,6 +104,7 @@ class _EmptyCopy extends StatelessWidget {
     required this.actionLabel,
     required this.actionKey,
     required this.onAction,
+    required this.footer,
   });
 
   final String title;
@@ -108,6 +112,7 @@ class _EmptyCopy extends StatelessWidget {
   final String? actionLabel;
   final Key? actionKey;
   final VoidCallback? onAction;
+  final Widget? footer;
 
   @override
   Widget build(BuildContext context) {
@@ -162,6 +167,7 @@ class _EmptyCopy extends StatelessWidget {
             ),
           ),
         ],
+        if (footer != null) ...[const SizedBox(height: 12), footer!],
       ],
     );
   }