Calmchy/Calmchy-NixOS ? reverse-engineered prompt

Build me a simple personal NixOS configuration from this repo.

I want a flake based setup that lets me manage my machine cleanly, with separate host config and reusable modules. Make it so I can install and update the system without a lot of manual tweaking, and include a setup script that helps get things running from a fresh clone.

Keep it practical and easy to extend later, since I may add more hosts or modules over time. If anything in the current NixOS docs has changed, look up the latest guidance online and use the right approach.

Please make the config feel ready for daily use, with sensible defaults and a clean structure, and leave it in a state where I can just adjust a few values for my own machine and rebuild.