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

modules/drivers/nvidia.nix

@@ -8,7 +8,7 @@
     open = true;
     nvidiaSettings = true;
     powerManagement.enable = false;
-    powerManagement.finegrained = false
+    powerManagement.finegrained = false;
     package = config.boot.kernelPackages.nvidiaPackages.latest;
   };