refactor(settings): collapse get_all to aksrt_settings and drop migration UI

Make aksrt_settings the sole theme settings store for get_all(), remove
aksrt_seo_settings/aksrt_basic_settings merge paths, point global.logo
schema at aksrt_settings, and delete the retired settings migration page,
route, REST endpoint, and related SPA surface.

inc/classes/settings/class-aksrt-settings-credits-payment-groups.php

@@ -86,7 +86,7 @@ trait AKSRT_Settings_Credits_Payment_Groups {
     /**
      * 邀请注册功能总开关（独立于积分系统）。
      * 控制邀请链接、注册页邀请码字段、用户中心邀请卡片的显示。
-     * 存储在 aksrt_basic_settings['invite_registration_enabled']。
+     * 存储在 aksrt_settings（invit_code_s / invite_registration_enabled）。
      */
     public static function invite_registration_enabled(): bool {
         return AKSRT_Settings_Credits_Runtime::invite_registration_enabled();

inc/classes/settings/class-aksrt-settings-credits-runtime.php

@@ -232,7 +232,7 @@ class AKSRT_Settings_Credits_Runtime {
     /**
      * 邀请注册功能总开关（独立于积分系统）。
      * 控制邀请链接、注册页邀请码字段、用户中心邀请卡片的显示。
-     * 存储在 aksrt_basic_settings['invite_registration_enabled']。
+     * 存储在 aksrt_settings（invit_code_s / invite_registration_enabled）。
      */
     public static function invite_registration_enabled(): bool {
         return !empty(self::get_invite_registration_config()['enabled']);

inc/classes/settings/class-aksrt-settings-display-page-groups.php

@@ -10,7 +10,7 @@ defined('ABSPATH') || exit;
 trait AKSRT_Settings_Display_Page_Groups {
 
     /**
-     * 获取 SEO 设置（从 aksrt_seo_settings option 读取）
+     * 获取 SEO 设置（从 aksrt_settings 读取）
      */
     public static function get_seo_settings(): array {
         $s = self::get_all();