feat: hierarchical group & permission model (v1.25.0)

- Add utils/groups.js: the group schema + inheritance resolver (god_admin,
  {site}_super_admin, {site}_hosts_*/{site}_apps_* aggregates, per-resource
  admin/access/<capability>, meta everyone/{site}_everyone). admin implies
  access; capabilities explicit; hosts/apps orthogonal; cross-site isolated.
- permission.js: recognize god_admin (legacy app_super_admin aliased) and add
  onResource/requireResource for resource-level checks + everyone meta grants.
- user.js isAdmin: recognize god_admin + site-scoped super/app-admin groups.
- Remove the standalone Groups page (nav + route + view); groups are managed on
  adopted Directory resources. Add a /docs/groups help link in the Directory
  toolbar (GROUPS.md copied into the SSO docs).
- tests/groups.test.js: full resolver coverage (15 tests).

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

nodejs/routes/index.js

@@ -188,10 +188,6 @@ router.get('/users/:uid', function(req, res, next) {
   res.render('profile', {...values});
 });
 
-router.get('/groups', function(req, res, next) {
-  res.render('groups', {...values});
-});
-
 router.get('/token', function(req, res, next) {
   res.render('token', {...values});
 });