Third-Party API Calls Blocked by CORS

1. Third-party API doesn't support CORS or doesn't include your domain
2. Calling API directly from React instead of through backend
3. Missing credentials in CORS request setup
4. Preflight OPTIONS request fails
5. API uses Authorization header without CORS config

Route through Supabase Edge Function as proxy:

// Frontend
const response = await fetch('/functions/v1/proxy-api', {
  method: 'POST',
  body: JSON.stringify({ url: 'https://api.example.com/data' })
});

// Edge Function
export default async (req) => {
  const { url } = await req.json();
  const response = await fetch(url);
  return response;
}