feat: database-backed cron job queue replacing JSON file system

Replace file-based JSON cron queue with DB-backed job queue (pp_cron_jobs,
pp_cron_schedules). New Domain\CronJob module: CronJobType (constants),
CronJobRepository (CRUD, atomic fetch, retry/backoff), CronJobProcessor
(orchestration with handler registration). Priority ordering guarantees
apilo_send_order (40) runs before sync tasks (50). Includes cron.php auth
protection, race condition fix in fetchNext, API response validation,
and DI wiring across all entry points. 41 new tests.

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

autoload/front/App.php

@@ -177,9 +177,10 @@ class App
       'ShopOrder' => function() {
         global $mdb;
         $orderRepo = new \Domain\Order\OrderRepository( $mdb );
+        $cronJobRepo = new \Domain\CronJob\CronJobRepository( $mdb );
         return new \front\Controllers\ShopOrderController(
           $orderRepo,
-          new \Domain\Order\OrderAdminService( $orderRepo )
+          new \Domain\Order\OrderAdminService( $orderRepo, null, null, null, $cronJobRepo )
         );
       },
       'ShopProducer' => function() {