fix(security): add CSRF protection to all POST endpoints + contract tests (B2)

CSRF guards added to 16 admin pages that previously accepted POST requests
without token verification (GR-SEC-001): departments, permissions, roles,
settings, tenants, users (create/edit/bulk/tokens), and lang switch.

New contract tests:
- PostEndpointCsrfContractTest: scans all pages/ for POST handlers and
  verifies checkCsrfToken is present (API/data endpoints exempt).
- DatabaseUpdatesContractTest: validates db/updates/ scripts follow naming
  convention and use idempotent SQL patterns (GR-CORE-010).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pages/admin/users/create().php

@@ -9,6 +9,7 @@ use MintyPHP\Service\Access\UiAccessService;
 use MintyPHP\Service\Access\UiCapabilityMap;
 use MintyPHP\Service\Access\UserAuthorizationPolicy;
 use MintyPHP\Service\CustomField\UserCustomFieldValueService;
+use MintyPHP\Session;
 use MintyPHP\Support\Flash;
 use MintyPHP\Support\Guard;
 
@@ -91,6 +92,12 @@ $form = [
     'active' => 1,
 ];
 
+if ($request->isMethod('POST') && !Session::checkCsrfToken()) {
+    Flash::error(t('Form expired, please try again'), 'admin/users/create', 'csrf_expired');
+    Router::redirect('admin/users/create');
+    return;
+}
+
 if ($request->hasBody('email')) {
     $post = $request->bodyAll();
     $input = $post;