commit remaining frontend updates

public/js/auth.js

@@ -20,6 +20,40 @@ async function doLogin() {
   }
 }
 
+async function doRegister() {
+  const user = document.getElementById('registerUser').value.trim();
+  const pass = document.getElementById('registerPass').value.trim();
+  const passConfirm = document.getElementById('registerPassConfirm').value.trim();
+  if (!user || !pass) { document.getElementById('registerError').textContent = '请输入用户名和密码'; return; }
+  if (pass !== passConfirm) { document.getElementById('registerError').textContent = '两次密码输入不一致'; return; }
+  try {
+    const res = await fetch(API + '/api/register', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ username: user, password: pass })
+    });
+    const data = await res.json();
+    if (!res.ok) { document.getElementById('registerError').textContent = data.error; return; }
+    showToast('注册成功，请登录');
+    showLoginPage();
+  } catch (e) {
+    document.getElementById('registerError').textContent = '网络错误';
+  }
+}
+
+function showRegisterPage() {
+  document.getElementById('registerError').textContent = '';
+  document.getElementById('registerUser').value = '';
+  document.getElementById('registerPass').value = '';
+  document.getElementById('registerPassConfirm').value = '';
+  showPage('registerPage');
+}
+
+function showLoginPage() {
+  document.getElementById('loginError').textContent = '';
+  showPage('loginPage');
+}
+
 function doLogout() {
   token = null;
   username = null;