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

flake.nix

@@ -12,7 +12,6 @@
       url = "github:nix-community/nixvim";
       inputs.nixpkgs.follows = "nixpkgs";
     };
-    flake-utils.inputs.nixpkgs.follows = "nixpkgs";
   };
 
   outputs =
@@ -51,7 +50,6 @@
           extraSpecialArgs = {
             inherit inputs outputs;
           };
-
           modules = [
             ./home-manager/home.nix
             { custom.sessionType = "wayland"; }