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-credits.php

@@ -22,8 +22,8 @@ if (!function_exists('aksrt_user_credits')) {
     function aksrt_user_credits(int $user_id = 0): int {
         if ($user_id <= 0) $user_id = get_current_user_id();
         if ($user_id <= 0) return 0;
-        if (!class_exists('AKSRT_Credits')) return 0;
-        return AKSRT_Credits::balance($user_id);
+        if (!class_exists('\AKSRT\Credits\Credits')) return 0;
+        return \AKSRT\Credits\Credits::balance($user_id);
     }
 }
 
@@ -69,9 +69,9 @@ if (!function_exists('aksrt_credits_label')) {
         if (isset($map[$reason])) {
             return $map[$reason];
         }
-        if (str_starts_with($reason, 'free_') && class_exists('AKSRT_Points_Free')) {
+        if (str_starts_with($reason, 'free_') && class_exists('\AKSRT\Credits\PointsFree')) {
             $key = substr($reason, 5);
-            $cat = AKSRT_Points_Free::catalog();
+            $cat = \AKSRT\Credits\PointsFree::catalog();
             if (isset($cat[$key][0])) {
                 return (string) $cat[$key][0];
             }