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.

src/AKSRT/Content/Pay.php

@@ -0,0 +1,33 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Content;
+
+defined('ABSPATH') || exit;
+
+class Pay {
+    use PayRest;
+    use PayOrders;
+    use PayHelpers;
+
+    private static $instance = null;
+
+
+
+    public static function get_instance(): self {
+        if (null === self::$instance) {
+            self::$instance = new self();
+        }
+        return self::$instance;
+    }
+
+
+
+    public function init(): void {
+        add_action('rest_api_init', [$this, 'register_routes']);
+        add_action('aksrt_order_paid', [$this, 'on_order_paid'], 15, 2);
+    }
+
+}