fix: set HOME=/home/node in openclaw image to prevent /.openclaw mkdir errors

packages/openclaw-image/default.nix

@@ -235,6 +235,9 @@ pkgs.dockerTools.buildLayeredImage {
       # PATH: standard dirs + Nix store bin dirs are appended by buildLayeredImage
       "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
       "NODE_ENV=production"
+
+      # Home directory (Docker User directive doesn't set HOME from /etc/passwd)
+      "HOME=/home/node"
     ];
   };
 }