fix: add flake.lock back and update host configs

- Added `flake.lock` to pin dependencies (nixpkgs, home-manager, nixvim, flake-utils, etc.)
- Cleaned up `.gitignore`: stop ignoring `*.lock`
- Removed unused `flake-utils.inputs.nixpkgs.follows`
- Nixstation host:
  - Removed `keychron.nix`, Wacom tablet config, and redundant session variables
  - Simplified GDM/GNOME configuration and XKB layout
  - Commented out virtualisation setup
- Common NVIDIA host config:
  - Added explicit kernel modules, parameters, blacklists, and kernel version
  - Ensured GNOME + GDM configuration present
  - Updated NVIDIA driver settings and CUDA support

hosts/common/nvidia/default.nix

@@ -5,7 +5,10 @@
   imports = [
     #  ./passthrough.nix
   ];
-
+  boot.kernelModules = [ "nvidia" ];
+  boot.kernelParams = ["nvidia-drm.modset=1"];
+  boot.blacklistedKernelModules = ["nouveau"];
+  boot.kernelPackages = pkgs.linuxPackages_6_12;
   hardware = {
     graphics = {
       enable = true;
@@ -18,7 +21,7 @@
     nvidia = {
       modesetting.enable = true;
       nvidiaSettings = true;
-      open = false; # keep it like that for now, unstable!!
+      open = false;
       package = pkgs.linuxPackages.nvidiaPackages.latest;
       powerManagement.enable = false;
       powerManagement.finegrained = false;
@@ -26,10 +29,15 @@
   };
 
   services = {
-    xserver = {
-      videoDrivers = [ "nvidia" ];
-    };
+   desktopManager.gnome.enable = true;
+   displayManager = {
+      gdm.enable = true;
+      gdm.wayland = true;
+      defaultSession = "gnome";
+   };
+   xserver.videoDrivers = [ "nvidia" ];
   };
+
   nixpkgs.config.cudaSupport = true;
   environment.systemPackages = with pkgs; [
     cudaPackages.cuda_nvcc