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>

CLAUDE.md

@@ -36,7 +36,7 @@ composer test
 
 PHPUnit 9.6 via `phpunit.phar`. Bootstrap: `tests/bootstrap.php`. Config: `phpunit.xml`.
 
-Current suite: **765 tests, 2153 assertions**.
+Current suite: **805 tests, 2253 assertions**.
 
 ### Creating Updates
 See `docs/UPDATE_INSTRUCTIONS.md` for the full procedure. Updates are ZIP packages in `updates/0.XX/`. Never include `*.md` files, `updates/changelog.php`, or root `.htaccess` in update ZIPs.
@@ -116,7 +116,7 @@ All legacy directories (`admin/controls/`, `admin/factory/`, `admin/view/`, `fro
 - Constructor DI with `$db` (Medoo instance)
 - Methods serve both admin and frontend (shared Domain, no separate services)
 
-**Domain Modules**: Article, Attribute, Banner, Basket, Cache, Category, Client, Coupon, Dashboard, Dictionaries, Integrations, Languages, Layouts, Newsletter, Order, Pages, PaymentMethod, Producer, Product, ProductSet, Promotion, Scontainers, Settings, ShopStatus, Transport, Update, User
+**Domain Modules**: Article, Attribute, Banner, Basket, Cache, Category, Client, Coupon, CronJob, Dashboard, Dictionaries, Integrations, Languages, Layouts, Newsletter, Order, Pages, PaymentMethod, Producer, Product, ProductSet, Promotion, Scontainers, Settings, ShopStatus, Transport, Update, User
 
 **Admin Controllers** (`autoload/admin/Controllers/`):
 - DI via constructor (repositories injected)