feat(scheduler): delete orphaned jobs and block editing of unregistered jobs

Adds deleteOrphanedJobs() to clean up stale job_keys during ensureSystemJobs, and prevents editing jobs that are no longer registered in the runtime registry.

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

pages/admin/scheduled-jobs/edit($id).php

@@ -20,6 +20,8 @@ if (!$job) {
     Router::redirect('admin/scheduled-jobs');
 }
 
+$isRegistered = $scheduledJobService->isRegistered((string) ($job['job_key'] ?? ''));
+
 $currentUserId = (int) ($session['user']['id'] ?? 0);
 $authorizationService = app(\MintyPHP\Service\Access\AuthorizationService::class);
 $canManage = $authorizationService->authorize(\MintyPHP\Service\Access\OperationsAuthorizationPolicy::ABILITY_ADMIN_JOBS_MANAGE, [
@@ -39,6 +41,12 @@ $form = [
 ];
 $errorBag = formErrors();
 
+if (!$isRegistered) {
+    $canManage = false;
+    $canRunNow = false;
+    $errorBag->addGlobal(t('This scheduled job is no longer registered and cannot be edited. It has been superseded by a newer version.'));
+}
+
 if (requestInput()->method() === 'POST') {
     if (!$canManage) {
         Guard::deny();