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.

src/AKSRT/Admin/Schema/SchemaToolsHealth.php

@@ -0,0 +1,29 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Admin\Schema;
+
+defined('ABSPATH') || exit;
+
+class SchemaToolsHealth {
+
+    public static function build(): array {
+        return [
+            'key'        => 'health',
+            'title'      => '健康检查',
+            'version'    => '1.0.0',
+            'option_key' => 'aksrt_settings',
+            'groups'     => [
+                ['key' => 'check', 'title' => '环境检查', 'fields' => [
+                    ['key' => 'php_version', 'label' => 'PHP 版本', 'type' => 'display', 'help' => '建议 7.4+'],
+                    ['key' => 'wp_version', 'label' => 'WordPress 版本', 'type' => 'display', 'help' => '建议 5.8+'],
+                    ['key' => 'memory_limit', 'label' => '内存限制', 'type' => 'display', 'help' => '建议 256M+'],
+                    ['key' => 'upload_max_size', 'label' => '上传限制', 'type' => 'display'],
+                    ['key' => 'extensions', 'label' => '必要扩展', 'type' => 'display', 'help' => 'curl, mbstring, json, gd'],
+                ]],
+            ],
+        ];
+    }
+}