dual check v0.1

client/lib/modules/dual_check/nickname_service.dart

@@ -0,0 +1,33 @@
+// 全局昵称设置
+// 持久化到 SharedPreferences / localStorage，所有工具共享同一个昵称
+import 'package:shared_preferences/shared_preferences.dart';
+
+const _keyNickname = 'toolbox.nickname';
+
+class NicknameService {
+  NicknameService._();
+  static final NicknameService instance = NicknameService._();
+
+  SharedPreferences? _prefs;
+
+  Future<void> _ensureInit() async {
+    _prefs ??= await SharedPreferences.getInstance();
+  }
+
+  /// 获取当前昵称，未设置时返回默认昵称
+  Future<String> get nickname async {
+    await _ensureInit();
+    final n = _prefs!.getString(_keyNickname);
+    if (n != null && n.trim().isNotEmpty) return n.trim();
+    return '用户';
+  }
+
+  /// 设置昵称（1-32 字符，过短返回 false）
+  Future<bool> setNickname(String value) async {
+    final trimmed = value.trim();
+    if (trimmed.isEmpty || trimmed.length > 32) return false;
+    await _ensureInit();
+    await _prefs!.setString(_keyNickname, trimmed);
+    return true;
+  }
+}