feat(client): 关于我们内容改用配置文件 + 窗口标题改岩美酒库

- 新增 assets/config/app_info.json（服务商/网站/邮箱真实值），启动时
  AppInfo.load() 读取，不硬编码、不走环境变量
- 关于我们/续费/反馈处的服务商、网站、邮箱统一读配置
- Windows 窗口标题 jiu_client -> 岩美酒库（u8 + UTF-8→UTF-16 防乱码）

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/core/config/app_info.dart

@@ -0,0 +1,28 @@
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+/// 应用「关于我们」等品牌信息，从配置文件 assets/config/app_info.json 读取，
+/// 不硬编码、不走环境变量。在 main() 启动时调用 [load] 加载一次。
+class AppInfo {
+  const AppInfo._();
+
+  static const _assetPath = 'assets/config/app_info.json';
+
+  static String provider = '';
+  static String website = '';
+  static String email = '';
+
+  /// 加载配置文件。失败时保留为空（不影响应用启动）。
+  static Future<void> load() async {
+    try {
+      final raw = await rootBundle.loadString(_assetPath);
+      final map = jsonDecode(raw) as Map<String, dynamic>;
+      provider = (map['provider'] as String?) ?? '';
+      website = (map['website'] as String?) ?? '';
+      email = (map['email'] as String?) ?? '';
+    } catch (e) {
+      debugPrint('AppInfo.load failed: $e');
+    }
+  }
+}