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/home-manager/styling.nix

@@ -1,7 +1,6 @@
 { pkgs, ... }:
 
 {
-  # set gtk theme
   gtk = {
     enable = true;
     theme = {
@@ -13,7 +12,6 @@
     gtk4.extraConfig.gtk-application-prefer-dark-theme = 1;
   };
 
-  # set qt theme
   qt = {
     enable = true;
     platformTheme.name = "qt6";
@@ -22,10 +20,4 @@
       package = pkgs.adwaita-qt;
     };
   };
-
-  # ensure packages are installed
-  home.packages = with pkgs; [
-    gnome-themes-extra
-    adwaita-qt
-  ];
 }