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/shortcodes/archive.php

@@ -2,8 +2,8 @@
 /**
  * Shortcode template: [aksrt_archive]
  *
- * 紧凑版文章归档（按年月分组）。供 AKSRT_Shortcodes::render_archive() 通过
- * AKSRT_Templates::render_archive_shortcode() 以输出缓冲方式 include。
+ * 紧凑版文章归档（按年月分组）。供 \AKSRT\Core\Shortcodes::render_archive() 通过
+ * \AKSRT\Core\Templates::render_archive_shortcode() 以输出缓冲方式 include。
  *
  * 可用变量：$attrs（短代码属性）、$content。
  *