Pass around `perSystem`'s `pkgs` instances to the system configurations
Some more refactoring in `configurations`' `mkHost` functions
Also start using `home-manager`'s `useGlobalPkgs` option
Also use `mkShellNoCC` for default `devShell`
Also `nix flake update`
Add separate module for `wireguard`
Rekey `jeeves_password` (use all `users`' keys)
Add secrets related to Wireguard: server public/private, cheetah public
Add a `.gitignore` for the private `limonka_age` key