fix(client): 商品公开页加载后更新浏览器标题为商品名称

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/screens/public/public_product_screen.dart

@@ -2,6 +2,7 @@ import 'dart:math' as math;
 import 'package:dio/dio.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:go_router/go_router.dart';
 import 'package:url_launcher/url_launcher.dart';
 import '../../core/config/app_config.dart';
@@ -54,6 +55,13 @@ class _PublicProductScreenState extends State<PublicProductScreen> {
       );
       final data = (resp.data as Map<String, dynamic>)['data'] as Map<String, dynamic>;
       setState(() { _data = data; _loading = false; });
+      // 更新浏览器标签标题（Flutter Web 会写 document.title）
+      final name = data['name'] as String? ?? '';
+      if (name.isNotEmpty) {
+        SystemChrome.setApplicationSwitcherDescription(
+          ApplicationSwitcherDescription(label: name, primaryColor: 0xFF8B2331),
+        );
+      }
     } catch (e) {
       setState(() { _error = e.toString(); _loading = false; });
     }