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.

image.php

@@ -7,8 +7,8 @@
 
 defined('ABSPATH') || exit;
 
-$system_tools = class_exists('AKSRT_Settings')
-    ? AKSRT_Settings::get_system_tools_settings()
+$system_tools = class_exists('\AKSRT\Settings\Settings')
+    ? \AKSRT\Settings\Settings::get_system_tools_settings()
     : ['close_attachment_page' => true];
 
 if (!empty($system_tools['close_attachment_page'])) {