refactor: flatten src/AKSRT → src (drop theme-identifier dir)

Move all domain folders from src/AKSRT/{Domain} to src/{Domain}; remap
Composer PSR-4 "AKSRT\\": "src/"; update audit script + README + ADR
paths; remove dead tools/build-psr4-map.php (scanned deleted inc/classes).

src/Admin/Schema/SchemaToolsImportExport.php

@@ -0,0 +1,29 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Admin\Schema;
+
+defined('ABSPATH') || exit;
+
+class SchemaToolsImportExport {
+
+    public static function build(): array {
+        return [
+            'key'        => 'import-export',
+            'title'      => '导入导出',
+            'version'    => '1.0.0',
+            'option_key' => 'aksrt_settings',
+            'groups'     => [
+                ['key' => 'export', 'title' => '导出配置', 'fields' => [
+                    ['key' => 'export_settings', 'label' => '导出主题设置', 'type' => 'button', 'help' => '导出当前所有主题配置为 JSON 文件'],
+                    ['key' => 'export_options', 'label' => '导出 WordPress 选项', 'type' => 'button', 'help' => '导出 aksrt_settings 等选项'],
+                ]],
+                ['key' => 'import', 'title' => '导入配置', 'fields' => [
+                    ['key' => 'import_settings', 'label' => '导入主题设置', 'type' => 'file', 'accept' => '.json', 'help' => '导入主题配置文件（将覆盖当前设置）'],
+                ]],
+            ],
+        ];
+    }
+}