add wallpapers to assets, fix nh cleaning job, reenable stylix

modules/features/applications/cli/nh.nix

@@ -19,7 +19,7 @@ in {
         extraArgs = lib.mkOption {
           type = lib.types.str;
           description = "Any extra arguments that should be passed to the `nh clean` command when it is called by this service.";
-          default = "--keep 10 --keep-since 7d";
+          default = "--keep 10 --keep-since 7d --optimise";
         };
       };
     };