feat: extract nvidia module and cleanup matej-nixos HW config

modules/nixos/nvidia.nix

@@ -0,0 +1,23 @@
+{
+  lib,
+  config,
+  ...
+}:
+{
+  options = {
+    nvidia.enable = lib.mkEnableOption "NVIDIA GPU support";
+  };
+
+  config = lib.mkIf config.nvidia.enable {
+    hardware.graphics.enable = true;
+
+    services.xserver.videoDrivers = [ "nvidia" ];
+
+    hardware.nvidia = {
+      modesetting.enable = true;
+      open = true;
+      nvidiaSettings = true;
+      package = config.boot.kernelPackages.nvidiaPackages.stable;
+    };
+  };
+}