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/thunar.nix

@@ -1,14 +1,9 @@
 { pkgs, ... }:
 
 {
-  # Enable Thunar
   programs.thunar.enable = true;
 
-  # Install Tumbler thumbnailer service
-  environment.systemPackages = with pkgs; [
-    tumbler
-  ];
-
-  # Ensure Thunar can locate the thumbnailer extensions
+  # thumbnails: tumbler service plus the path it loads extensions from
+  environment.systemPackages = [ pkgs.tumbler ];
   environment.pathsToLink = [ "share/thumbnailers" ];
 }