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/shop/product-cat.php

@@ -12,7 +12,7 @@ get_header();
 $term    = get_queried_object();
 $paged   = max(1, (int) get_query_var('paged'));
 $orderby = isset($_GET['shop_orderby']) ? sanitize_key(wp_unslash((string) $_GET['shop_orderby'])) : '';
-$shop    = class_exists('AKSRT_Shop') ? AKSRT_Shop::get_instance() : null;
+$shop    = class_exists('\AKSRT\Shop\Shop') ? \AKSRT\Shop\Shop::get_instance() : null;
 $view    = $shop ? $shop->get_product_archive_view([
     'taxonomy' => 'aksrt_product_cat',
     'term_id'  => $term ? (int) $term->term_id : 0,