refactor(autoload): migrate theme classes to Composer PSR-4

Move 288 types from global AKSRT_* + inc/classes manual requires into
namespace AKSRT\{Domain} under src/AKSRT/, wire composer.json psr-4,
and slim bootstrap to helpers/modules/hooks only. Split multi-class
widget/gateway files, update admin contract audit paths, and document
the layout in ADR/README.

templates/parts/shop/product-card.php

@@ -3,7 +3,7 @@
  * Shared product card (archive / related / storefront).
  *
  * Expected args:
- * - product: array from AKSRT_Shop::build_product_card_view()
+ * - product: array from \AKSRT\Shop\Shop::build_product_card_view()
  * - show_sales: bool (optional)
  * - sales_cfg: array (optional; used when show_sales not provided)
  *