refactor: simplify Nix configuration and update dependencies

Replaced custom Nerd Fonts overrides with predefined ones. Removed unused Neovim settings and plugins, and disabled Neovim for a specific user. Updated various flake dependencies to their latest versions.

modules/nixos/services/gui/default.nix

@@ -1,9 +1,8 @@
-{
-  options,
-  config,
-  lib,
-  pkgs,
-  ...
+{ options
+, config
+, lib
+, pkgs
+, ...
 }:
 
 with lib;
@@ -164,7 +163,6 @@ in
         tmux
         vim
         wl-clipboard
-        yubikey-manager-qt
         yubikey-personalization
         zellij
       ]
@@ -184,13 +182,9 @@ in
         noto-fonts-emoji
         liberation_ttf
         freefont_ttf
-        (nerdfonts.override {
-          fonts = [
-            "FiraCode"
-            "DroidSansMono"
-            "JetBrainsMono"
-          ];
-        })
+        nerd-fonts.fira-code
+        nerd-fonts.droid-sans-mono
+        nerd-fonts.jetbrains-mono
       ];
 
       fontconfig = {