add qt dark theme

modules/core/default.nix

@@ -5,6 +5,7 @@
     ./boot.nix
     ./env-vars.nix
     ./nix-settings.nix
+    ./qt.nix
     ./security.nix
     ./time.nix
     ./users.nix

modules/core/qt.nix

@@ -0,0 +1,18 @@
+{ ... }:
+
+{
+  qt = {
+    enable = true;
+    platformTheme = "gnome";
+    style = "adwaita-dark";
+  };
+
+  environment.systemPackages = with pkgs; [
+    adwaita-qt
+  ];
+  
+  xdg.portal = {
+    enable = true;
+    extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
+  };
+}