Enhance: platform order create flow carries back and redirects with back

app/Http/Controllers/Admin/PlatformOrderController.php

@@ -38,6 +38,8 @@ class PlatformOrderController extends Controller
             'discount_amount' => (float) $request->query('discount_amount', 0),
             'payment_channel' => (string) $request->query('payment_channel', ''),
             'remark' => (string) $request->query('remark', ''),
+            // back：用于创建成功后回到来源页（例如订阅详情）
+            'back' => (string) $request->query('back', ''),
         ];
 
         $siteSubscription = null;
@@ -69,6 +71,7 @@ class PlatformOrderController extends Controller
             'discount_amount' => ['nullable', 'numeric', 'min:0'],
             'payment_channel' => ['nullable', 'string', 'max:30'],
             'remark' => ['nullable', 'string', 'max:2000'],
+            'back' => ['nullable', 'string', 'max:2000'],
         ]);
 
         $plan = Plan::query()->findOrFail((int) $data['plan_id']);
@@ -122,7 +125,15 @@ class PlatformOrderController extends Controller
             'remark' => $data['remark'] ?? null,
         ]);
 
-        return redirect('/admin/platform-orders/' . $order->id)
+        $back = (string) ($data['back'] ?? '');
+        $safeBack = str_starts_with($back, '/') ? $back : '';
+
+        $redirectUrl = '/admin/platform-orders/' . $order->id;
+        if ($safeBack !== '') {
+            $redirectUrl .= '?back=' . urlencode($safeBack);
+        }
+
+        return redirect($redirectUrl)
             ->with('success', '平台订单已创建：' . $order->order_no . '（待支付/待生效）');
     }