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.

inc/helpers/aksrt-archive.php

@@ -16,8 +16,8 @@ if (!function_exists('aksrt_archive_get_list_style_settings')) :
 	 * @return array<string,mixed>
 	 */
 	function aksrt_archive_get_list_style_settings(): array {
-		$settings = class_exists('AKSRT_Settings')
-			? AKSRT_Settings::get_post_list_style_settings()
+		$settings = class_exists('\AKSRT\Settings\Settings')
+			? \AKSRT\Settings\Settings::get_post_list_style_settings()
 			: [];
 
 		return [
@@ -184,8 +184,8 @@ if (!function_exists('aksrt_resolve_post_list_render_config')) :
 		];
 
 		// Multi-thumb from global thumb settings + category allowlist.
-		if (class_exists('AKSRT_Settings')) {
-			$thumb_settings = AKSRT_Settings::get_post_thumb_settings();
+		if (class_exists('\AKSRT\Settings\Settings')) {
+			$thumb_settings = \AKSRT\Settings\Settings::get_post_thumb_settings();
 			if (!empty($thumb_settings['multi_enabled'])) {
 				$config['multi_thumb_enabled'] = true;
 				$config['multi_thumb_limit'] = (int) ($thumb_settings['multi_count'] ?? 4);