Platform orders index: use BackUrl for current subscription link

resources/views/admin/platform_orders/index.blade.php

@@ -81,10 +81,11 @@
             <div class="muted">当前已锁定订阅：</div>
             <div>
                 @php
-                    $subShowUrl = '/admin/site-subscriptions/' . $currentSubscription->id;
-                    $subShowUrl .= '?' . \Illuminate\Support\Arr::query([
-                        'back' => $selfWithoutBack,
-                    ]);
+                    // 订阅详情链接：附带 back 回到本页（剔除 back，避免嵌套膨胀），并统一走 BackUrl helper。
+                    $subShowUrl = \App\Support\BackUrl::withBack(
+                        '/admin/site-subscriptions/' . $currentSubscription->id,
+                        $selfWithoutBack
+                    );
                 @endphp
                 <a class="link" href="{!! $subShowUrl !!}">{{ $currentSubscription->subscription_no }}</a>
                 <span class="muted">（订阅ID：{{ $currentSubscription->id }}）</span>