updates again

Signed-off-by: Michael Thomson <michael@michaelthomson.dev>

hosts/macbook/configuration.nix

@@ -6,6 +6,7 @@
 }: {
   imports = [
     inputs.home-manager.darwinModules.default
+    ../../modules/nix-darwin/system.nix
   ];
 
   nixpkgs.hostPlatform = "aarch64-darwin";
@@ -53,6 +54,7 @@
     extraSpecialArgs = {inherit inputs;};
     useGlobalPkgs = true;
     useUserPackages = true;
+    backupFileExtension = "backup";
     users = {
       mthomson = import ./home.nix;
     };