add user and packages modules

modules/default.nix

@@ -0,0 +1,8 @@
+{ self, inputs, ... }: {
+  flake.nixosConfigurations.nerv = inputs.nixpkgs.lib.nixosSystem {
+    modules = with self.nixosModules; [
+      user
+      packages
+    ];
+  };
+}