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/parts/single-author-bar.php

@@ -43,7 +43,7 @@ $abs_fmt = $use_modified
 $time_text = human_time_diff($rel_base, $now) . $rel_label;
 
 $classes = trim('article-avatar ' . $extra_class);
-$aksrt_pm_on = class_exists('AKSRT_Settings') && !empty(AKSRT_Settings::private_message_settings()['enabled']);
+$aksrt_pm_on = class_exists('\AKSRT\Settings\Settings') && !empty(\AKSRT\Settings\Settings::private_message_settings()['enabled']);
 $aksrt_msg_url = function_exists('aksrt_get_messages_page_url') ? aksrt_get_messages_page_url() : '';
 $login_url = function_exists('aksrt_get_login_url') ? aksrt_get_login_url() : wp_login_url(get_permalink());
 $is_self = is_user_logged_in() && get_current_user_id() === $author_id;
@@ -115,8 +115,8 @@ $is_self = is_user_logged_in() && get_current_user_id() === $author_id;
 								</a>
 							<?php else : ?>
 								<?php
-								$aksrt_post_settings = class_exists('AKSRT_Settings') && method_exists('AKSRT_Settings', 'get_post_page_settings')
-									? AKSRT_Settings::get_post_page_settings()
+								$aksrt_post_settings = class_exists('\AKSRT\Settings\Settings') && method_exists('\AKSRT\Settings\Settings', 'get_post_page_settings')
+									? \AKSRT\Settings\Settings::get_post_page_settings()
 									: [];
 								$rewards_on = !empty($aksrt_post_settings['rewards_enabled'])
 									|| !empty($aksrt_post_settings['post_rewards_enabled'])