Binance 不允许带自定义 Header 的跨域请求。解决方法：部署免费 Cloudflare Worker 中转：

1. 注册 Cloudflare Workers（免费）
2. 新建 Worker，粘贴下面代码，点「保存并部署」
3. 验证：浏览器打开 https://你的worker地址/api/v3/ping，应返回 {}
4. 将 Worker 域名填到上面「代理地址」框

export default {
  async fetch(request) {
    if (request.method === 'OPTIONS') {
      return new Response(null, { headers: {
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Headers': '*',
        'Access-Control-Allow-Methods': 'GET,POST,DELETE,PUT,OPTIONS',
      }});
    }
    const url = new URL(request.url);
    const target = (url.pathname.startsWith('/fapi/') ? 'https://fapi.binance.com' : 'https://api.binance.com') + url.pathname + url.search;
    const headers = new Headers();
    const apiKey = request.headers.get('X-MBX-APIKEY');
    if (apiKey) headers.set('X-MBX-APIKEY', apiKey);
    const reqBody = ['GET','HEAD'].includes(request.method) ? undefined : await request.arrayBuffer();
    if (request.headers.get('Content-Type')) headers.set('Content-Type', request.headers.get('Content-Type'));
    const res = await fetch(target, { method: request.method, headers, body: reqBody });
    const body = await res.text();
    return new Response(body, {
      status: res.status,
      headers: {
        'Content-Type': res.headers.get('Content-Type') || 'application/json',
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Headers': '*',
      },
    });
  }
};