chore: drop redundant packages and options

- packages.nix is the baseline: drop neovim (nixvim), nvd, sof-firmware (enableAllFirmware), qtmultimedia (v4 leftover); vial moves to vial.nix, wl-clipboard to noctalia.nix, claude-code becomes a plain package here
- drop packages and options already provided elsewhere: noctalia (home-manager), gnupg/pinentry-qt (agent), gtk/qt themes, sddm Theme.Current, zsh plugins (home-manager), group = users, empty firewall lists
- single-package lists without `with pkgs;`, steam package inside its block

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

modules/nixos/users.nix

@@ -1,10 +1,8 @@
 { pkgs, ... }:
 
 {
-  # create users
   users.users.aaron = {
     isNormalUser = true;
-    group = "users";
     extraGroups = [
       "wheel"
       "networkmanager"
@@ -13,10 +11,6 @@
     shell = pkgs.zsh;
   };
 
-  # add default zsh config
-  programs.zsh = {
-    enable = true;
-    enableCompletion = true;
-    autosuggestions.enable = true;
-  };
+  # login shell; plugins and prompt are configured in home-manager
+  programs.zsh.enable = true;
 }