async function doLogin() {
  const user = document.getElementById('loginUser').value.trim();
  const pass = document.getElementById('loginPass').value.trim();
  if (!user || !pass) { document.getElementById('loginError').textContent = '请输入用户名和密码'; return; }
  try {
    const res = await fetch(API + '/api/login', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ username: user, password: pass })
    });
    const data = await res.json();
    if (!res.ok) { document.getElementById('loginError').textContent = data.error; return; }
    token = data.token;
    username = data.username;
    localStorage.setItem('token', token);
    localStorage.setItem('username', username);
    showPage('homePage');
  } catch (e) {
    document.getElementById('loginError').textContent = '网络错误';
  }
}

function doLogout() {
  token = null;
  username = null;
  localStorage.removeItem('token');
  localStorage.removeItem('username');
  showPage('loginPage');
}