feat: use a slightly different config for testing and production

[AshesOfEther]

This is useful for things where we need to have a slightly different configuration for testing locally. Currently it's primarily for the domain name, but it will likely also prove useful for things like Stregsystemet, where we want to use test data locally and then real data in production.

[Mast3rwaf1z]

Looks good, I would just call prod fklub instead of fklub-prod for consistency with hostname, since my own systems choose their flake based on hostname. This obvs doesn't matter if we're deploying in GitHub actions anyway tho. Up to you.