You're running into the same issue I had to deal with recently. You're going to be rejected by Cookies Policy and your backend server CORS policy. I don't think you have you have server side CORS setup correctly since it's giving you nothing. I can't see your backend CORS Middleware since it's not presented.

The second thing you're going to run into is Cookie Policy and it's incredibly unforgiving also. If the domain for the server and the receiver server do not match then it will dump the cookie as a measure of safety.

I can help with your server side cookie issue if you tell me what backend you're running. Once you start getting a cookie back on Svelte I can help with sending the cookie back to the backend server.