feat(jeeves): wireguard

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

machines/nixos/x86_64-linux/jeeves/network.nix

@@ -3,7 +3,6 @@
   environment.systemPackages = with pkgs; [
   ];
 
-  # Networking
   age.secrets."home/wifi.env".file = ../../../../secrets/home/wifi.env.age;
   networking.wireless = {
     iwd.enable = true;