fix: 完善用户路由和注册回调

- App.tsx 导入 hasValidUserSession 修复 TS 编译错误
- UserRegister 增加 onLogin 回调，注册成功自动跳转

src/web/pages/UserRegister.tsx

@@ -2,7 +2,7 @@ import React, { useState } from 'react';
 import { useNavigate, Link } from 'react-router-dom';
 import { persistUserSession } from '../authSession.js';
 
-export default function UserRegister() {
+export default function UserRegister({ onLogin }: { onLogin?: () => void }) {
   const navigate = useNavigate();
   const [username, setUsername] = useState('');
   const [email, setEmail] = useState('');
@@ -36,6 +36,7 @@ export default function UserRegister() {
       }
       const result = await res.json();
       persistUserSession(localStorage, result.token);
+      onLogin?.();
       navigate('/user/dashboard');
     } catch (err: any) {
       setError(err?.message || '注册失败');