fix(vip): preserve layered membership expirations

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Admin/Schema/SchemaPayment.php

@@ -129,7 +129,7 @@ class SchemaPayment {
                         ]],
                         ['key' => 'points_exchange', 'title' => '积分兑换会员', 'fields' => [
                             ['key' => 'pay_vip_points_exchange_s', 'label' => '启用积分兑换', 'type' => 'switch', 'default' => false],
-                            ['key' => 'payment_vip_points_packages', 'label' => '兑换套餐', 'type' => 'textarea', 'default' => "1|500|30|积分月卡\n1|5000|0|积分永久", 'dependsOn' => ['key' => 'pay_vip_points_exchange_s', 'value' => true], 'help' => '每行：等级|积分|天数|标题（天数 0=永久；仅未开通会员可兑）'],
+                            ['key' => 'payment_vip_points_packages', 'label' => '兑换套餐', 'type' => 'textarea', 'default' => "1|500|30|积分月卡\n1|5000|0|积分永久", 'dependsOn' => ['key' => 'pay_vip_points_exchange_s', 'value' => true], 'help' => '每行：等级|积分|天数|标题（天数 0=永久；普通用户可开通，已有会员可续费同等级或升级更高等级）'],
                             ['key' => 'pay_vip_points_exchange_desc', 'label' => '兑换说明', 'type' => 'textarea', 'default' => '', 'dependsOn' => ['key' => 'pay_vip_points_exchange_s', 'value' => true]],
                         ]],
                         ['key' => 'benefit', 'title' => '下载权益', 'fields' => [