fix(ai): treat unchanged AI settings as successful save

update_option returns false when values are identical, which made
POST /ai/settings respond 400 with "保存失败" on no-op saves and
masked-key re-saves. Normalize config, accept no-op as success, and
only send a new API key from the admin form when entered.

inc/classes/admin/class-aksrt-admin-ai-controller.php

@@ -130,7 +130,10 @@ class AKSRT_Admin_AI_Controller extends AKSRT_Admin_Controller_Base {
 
         $success = AKSRT_AI::get_instance()->update_config($config);
         if ($success) {
-            return $this->success(['message' => __('AI 设置已保存', 'aksrt')]);
+            return $this->success([
+                'message' => __('AI 设置已保存', 'aksrt'),
+                'data'    => AKSRT_AI::get_instance()->get_status(),
+            ]);
         }
         return $this->error(__('保存失败', 'aksrt'));
     }