Cannot talk to OIDC server which is reachable only through pangolin

Hi,

I was very excited to see the OIDC support in Pangolin and needed to test it out. Integration was simple enough, but login did not succeed.

My OIDC server (PocketID) is itself reachable through Pangolin. When I access it via a browser it is working just fine.

However, when I try to login through it in Pangolin, I'm getting a timeout error after 10s after the successful authorization:

Note that PocketID itself is working fine with other services.

In the log, I see this error message:
```
2025-05-04T15:35:32.840Z [error]: Failed to send request
Stack: Error: Failed to send request
at sendTokenRequest (file:///app/node_modules/arctic/dist/request.js:35:15)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async OAuth2Client.validateAuthorizationCode (file:///app/node_modules/arctic/dist/client.js:66:24)
at async cg (file:///app/dist/server.mjs:31:142009)
```

Is this a known / expected limitation, or is there something I'm missing?

Thanks!