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/tenants/edit($id).php

@@ -5,6 +5,7 @@ use MintyPHP\Http\SessionStoreInterface;
 use MintyPHP\Router;
 use MintyPHP\Service\Access\TenantAuthorizationPolicy;
 use MintyPHP\Service\CustomField\TenantCustomFieldService;
+use MintyPHP\Session;
 use MintyPHP\Support\Flash;
 use MintyPHP\Support\Guard;
 
@@ -95,6 +96,12 @@ $errorBag = formErrors();
 $errors = [];
 $form = array_merge($tenant, $ssoConfig);
 
+if ($request->isMethod('POST') && !Session::checkCsrfToken()) {
+    Flash::error(t('Form expired, please try again'), "admin/tenants/edit/{$uuid}", 'csrf_expired');
+    Router::redirect("admin/tenants/edit/{$uuid}");
+    return;
+}
+
 if ($request->hasBody('description')) {
     $post = $request->bodyAll();
     $submitDecision = $authorizationService->authorize(TenantAuthorizationPolicy::ABILITY_ADMIN_TENANTS_EDIT_SUBMIT, [