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/pages/page-special.php

@@ -3,7 +3,7 @@
  * Template Name: AKSRT - Special Page
  *
  * 专题聚合页模板 — 用于内容专题、活动页、产品介绍页等。
- * 读取 AKSRT_Settings 中的 page_display.special 配置，支持 per-page meta 覆盖。
+ * 读取 \AKSRT\Settings\Settings 中的 page_display.special 配置，支持 per-page meta 覆盖。
  *
  * @package AKSRT
  */
@@ -15,8 +15,8 @@ get_header();
 $post_id = get_the_ID();
 
 // 从门面 getter 读取专题页设置（validated & sanitized）
-$special = class_exists('AKSRT_Settings')
-	? AKSRT_Settings::get_special_page_settings()
+$special = class_exists('\AKSRT\Settings\Settings')
+	? \AKSRT\Settings\Settings::get_special_page_settings()
 	: [];
 
 $defaults = [