Use home-manager.sharedModules for shared user config

Replace manual forEachUser pattern with built-in sharedModules for
applying config to all home-manager users. Add automatic garbage
collection of old generations (weekly, older than 7 days) and remove
the now-unnecessary expire-home-manager-generations justfile recipe.

Also update codex PR patch hash (upstream patch was modified).

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

nixos/base.nix

@@ -93,6 +93,5 @@ makeEnable config "myModules.base" true {
 
   programs.dconf.enable = true;
 
-  home-manager.users = forEachUser (import ./home-manager.nix);
   nix.settings.trusted-users = realUsers ++ ["gitea-runner"];
 }

nixos/flake.nix

@@ -155,7 +155,7 @@
       }
       {
         pr = 483705; # codex: 0.89.0 -> 0.92.0
-        hash = "sha256-tkZP0ATAAuBNnJGo+xjXJD0byXAgeKoB+U3ZUaoCTHM=";
+        hash = "sha256-ZaiuRfl7gei0AyjPvLJidP3qfIaNbrvKROhKwmoiE5o=";
       }
       # claude-code
       # {

nixos/home-manager.nix

@@ -1,5 +1,12 @@
 { pkgs, ... }:
 {
+  # Automatic garbage collection of old home-manager generations
+  nix.gc = {
+    automatic = true;
+    dates = "weekly";
+    options = "--delete-older-than 7d";
+  };
+
   xdg.configFile."greenclip.toml".text = ''
     [greenclip]
       history_file = "~/.cache/greenclip.history"

nixos/justfile

@@ -3,12 +3,3 @@ switch *args:
 
 fix-local-path-issue:
 	nix flake update imalison-taffybar
-
-
-expire-home-manager-generations:
-	#!/usr/bin/env bash
-	set -euxo pipefail
-	for user in $(awk -F':' '{ if ($3 >= 1000 && $7 !~ /nologin|false|sync|shutdown|halt/) print $1 }' /etc/passwd); do
-	    echo $user
-	    sudo su - $user -c 'home-manager expire-generations -1days'
-	done

nixos/nix.nix

@@ -19,6 +19,7 @@
     home-manager.useGlobalPkgs = true;
     home-manager.useUserPackages = true;
     home-manager.backupFileExtension = "backup";
+    home-manager.sharedModules = [ ./home-manager.nix ];
 
     nix = rec {
       extraOptions = ''