chore: split nixos and opentofu

nixos/hosts/Builder/default.nix

@@ -0,0 +1,50 @@
+{ pkgs, ... }:
+
+{
+  config = {
+    networking = {
+      hostName = "Builder";
+      hostId = "aaaa4200";
+      domain = "depeuter.dev";
+
+      useDHCP = false;
+      enableIPv6 = true;
+
+      defaultGateway = {
+        address = "192.168.0.1";
+        interface = "ens18";
+      };
+
+      interfaces.ens18 = {
+        ipv4.addresses = [
+          {
+            address = "192.168.0.42";
+            prefixLength = 24;
+          }
+        ];
+      };
+
+      nameservers = [
+        "1.1.1.1"
+        "1.0.0.1"
+      ];
+    };
+
+    # Dedicated builder user
+    users.users.builder = {
+      isNormalUser = true;
+      description = "Nix Remote Builder";
+      # You must add the public key corresponding to `builder-ssh-key` here
+      openssh.authorizedKeys.keys = [
+        "ssh-ed25519 AAAAC3NzaC1... TODO: replace with build-farm-key.pub"
+      ];
+    };
+
+    # Optimize nix settings for a build farm
+    nix.settings.trusted-users = [ "builder" ];
+    nix.settings.cores = 0; # Use all cores
+    nix.settings.max-jobs = "auto";
+
+    system.stateVersion = "24.05";
+  };
+}