chore(nix): add evil-helix package and trusted-users setting

Add pkgs.evil-helix_git to the home environment so the helix-based
editor is available for the user.

Configure nix.settings.trusted-users to include "root" and "@wheel" so
the wheel group is treated as trusted users for Nix system operations.

nixos/users/default.nix

@@ -21,6 +21,11 @@
     shell = pkgs.zsh;
   };
 
+  nix.settings.trusted-users = [
+    "root"
+    "@wheel"
+  ];
+
   programs.nh = {
     enable = true;
     clean.enable = true;