Enhance: plans index show safe back link

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

@@ -29,6 +29,16 @@
 <div class="card mb-20">
     <p class="muted muted-tight">这里是总台视角的套餐目录页，用于沉淀平台可售卖的标准能力包。</p>
     <p class="muted">当前阶段先完成套餐主数据可见、可筛与口径收拢，后续再接授权项、售价规则与上下架动作。</p>
+
+    @php
+        $incomingBack = (string) request()->query('back', '');
+        $safeBack = str_starts_with($incomingBack, '/') ? $incomingBack : '';
+    @endphp
+    @if($safeBack)
+        <div class="mt-10">
+            <a href="{{ $safeBack }}" class="muted">← 返回上一页（保留上下文）</a>
+        </div>
+    @endif
 </div>
 
 <div class="card mb-20">