Update Zerl version and client build system

[z-silver]

This should make things Just Work^TM for the most part. It also eliminates some kludges and generally streamlines things.

How to test: run just client inside the flake. Maybe run the server as well and connect to it if you're feeling particularly paranoid.

[EduardoLR10]

I would like to have a list of things in the PR description that I should test locally to verify all the changes. Is just client enough within Nix or is something else needed?

[z-silver]

I would like to have a list of things in the PR description that I should test locally to verify all the changes. Is just client enough within Nix or is something else needed?

That should be enough, but you can also run the backend and try connecting to it if you're feeling paranoid. (I updated the PR description as well.)