document.getElementById('contact-form').addEventListener('submit', function (e) {
  e.preventDefault();
  const btn = this.querySelector('button[type="submit"]');
  btn.disabled = true;
  const msg = document.getElementById('form-msg');
  msg.textContent = '感谢提交！我们将尽快联系您。';
  setTimeout(() => { btn.disabled = false; msg.textContent = ''; }, 3000);
});