Signed and encrypted JWT with LetsEncrypt certificate. Is it possible?

Hello, I am experimenting with a self-hosted Zitadel+PostgreSQL, so this might be a noob question. What I am trying to achieve is to develop custom login UIs for stateless apps, in Svelte and Flutter (SSO is a requirement), which, after login and password authentication, get a JWT, both signed and encrypted using my own LetsEncrypt certificate.

1) Is it possible to configure the certificate in Zitadel using an API call (GPT-4 says that the endpoint is https://<YOUR_ZITADEL_DOMAIN>/management/v1/projects/<PROJECT_ID>/keys but I can´t find it in the docs and I get a 404)

2) Is it possible to configure Zitadel to return as a product of the auth flow the signed and encrypted JWT?

Thanks.