chore: clean up and optimize nixos configuration

- fix: nvidia.nix missing semicolon (build error)
- remove: ranger, vim from core/pkg.nix (yazi + neovim covers)
- remove: htop duplicate in home/pkg.nix (keep in system)
- replace: neofetch with fastfetch in home/pkg.nix
- remove: nixd LSP, keep nil only in nvchad.nix
- remove: empty server/pkg.nix and no-op server/firewall.nix
- remove: redundant services.pulseaudio.enable = false default
- add: comprehensive README.md documenting architecture

hosts/desktop/configuration.nix

@@ -6,25 +6,17 @@
     ../../modules/drivers/nvidia.nix
     ../../modules/drivers/amdgpu.nix
   ];
+
   # Bootloader.
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
-  
-  
-  # Enable CUPS to print documents.
-  # services.printing.enable = true;
 
   # Enable sound with pipewire.
-  services.pulseaudio.enable = false;
   security.rtkit.enable = true;
   services.pipewire = {
     enable = true;
     alsa.enable = true;
     alsa.support32Bit = true;
     pulse.enable = true;
-    # If you want to use JACK applications, uncomment this
-    #jack.enable = true;
   };
-  
-  
 }