Add codex 0.92.0 PR patch and fix deprecation warnings

- Add nixpkgs PR 483705 to bump codex from 0.89.0 to 0.92.0
- Disable overlay version overrides in favor of PR patches
- Replace deprecated pkgs.system with pkgs.stdenv.hostPlatform.system
- Replace deprecated xfce.thunar with thunar

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nixos/electron.nix

@@ -8,7 +8,7 @@ makeEnable config "myModules.electron" false {
     # keybase-gui
     zoom-us
   ];
-  home-manager.users = forEachUser (if pkgs.system == "x86_64-linux" then {
+  home-manager.users = forEachUser (if pkgs.stdenv.hostPlatform.system == "x86_64-linux" then {
     # systemd.user.services.bitwarden = {
     #   Unit = {
     #     Description = "Bitwarden";