feat: 实现密码重置功能与用户搜索API，优化注册登录流程

- 新增忘记密码页面与重置密码确认流程（前端+后端）
- 修复注册验证码页登录跳转路由
- 新增用户搜索API（按邮箱查询）
- 简化infra脚本，统一为app.sh
- 补充密码重置与用户API测试覆盖
- 更新runtime文档与AGENTS配置

apps/lib/features/auth/data/models/signup_request.dart

@@ -2,17 +2,20 @@ class SignupStartRequest {
   final String username;
   final String email;
   final String password;
+  final String? inviteCode;
 
   const SignupStartRequest({
     required this.username,
     required this.email,
     required this.password,
+    this.inviteCode,
   });
 
   Map<String, dynamic> toJson() => {
     'username': username,
     'email': email,
     'password': password,
+    if (inviteCode != null) 'invite_code': inviteCode,
   };
 }