async function apiDownload(path, method) {  // 二进制直出（联系人导出/模板）：失败时服务端回信封 JSON，成功返回 blob
  const opt = { method: method || 'GET' };
  if (TOKEN()) opt.headers = { Authorization: 'Bearer ' + TOKEN() };
  const res = await fetch(API_BASE + path, opt);
  const ct = res.headers.get('Content-Type') || '';
  if (ct.indexOf('json') >= 0) {
    const body = await res.json();
    const e = new Error(body.message || '下载失败'); e.code = body.code; throw e;
  }
  if (!res.ok) throw new Error('HTTP ' + res.status);
  return res.blob();
}