feat(PABU): cleanup and add deploy helper

hosts/PABU/system.nix

@@ -0,0 +1,27 @@
+{ lib, pkgs, ... }: {
+
+  # Installing a new system within the nspawn means that the /sbin/init script
+  # just needs to be updated, as there is no bootloader.
+  system.build.installBootLoader = pkgs.writeScript "install-sbin-init.sh" ''
+    #!${pkgs.runtimeShell}
+    ${pkgs.coreutils}/bin/ln -fs "$1/init" /sbin/init
+  '';
+
+  system.activationScripts.installInitScript = lib.mkForce ''
+    ${pkgs.coreutils}/bin/ln -fs $systemConfig/init /sbin/init
+  '';
+
+  boot.isContainer = true;
+
+  nix = {
+    settings = {
+      experimental-features = [ "nix-command" "flakes" ];
+      auto-optimise-store = true;
+    };
+  };
+
+  security.sudo.wheelNeedsPassword = false;
+
+  system.stateVersion = "24.05";
+
+}