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/profile.php

@@ -2,8 +2,8 @@
 /**
  * Shortcode template: [aksrt_profile]
  *
- * 当前登录用户的资料卡。供 AKSRT_Shortcodes::render_profile() 通过
- * AKSRT_Templates::render_profile_shortcode() 以输出缓冲方式 include。
+ * 当前登录用户的资料卡。供 \AKSRT\Core\Shortcodes::render_profile() 通过
+ * \AKSRT\Core\Templates::render_profile_shortcode() 以输出缓冲方式 include。
  *
  * 可用变量：$attrs（短代码属性，支持 user="<ID 或 login>" 指定用户）、$content。
  *
@@ -37,7 +37,7 @@ $home_url  = function_exists('aksrt_get_user_home_url') ? aksrt_get_user_home_ur
 $credits   = function_exists('aksrt_user_credits') ? (int) aksrt_user_credits($user_id) : 0;
 $post_count = (int) count_user_posts($user_id, 'post', true);
 $bio       = (string) get_the_author_meta('description', $user_id);
-$show_credits = class_exists('AKSRT_Settings') ? AKSRT_Settings::credits_enabled() : true;
+$show_credits = class_exists('\AKSRT\Settings\Settings') ? \AKSRT\Settings\Settings::credits_enabled() : true;
 ?>
 <div class="aksrt-profile-card aksrt-profile-card--shortcode">
 	<a class="aksrt-profile-card__avatar" href="<?php echo esc_url($home_url); ?>">