refactor: PlatformOrderController refundTotalForOrder use model refundTotal

app/Http/Controllers/Admin/PlatformOrderController.php

@@ -1488,20 +1488,8 @@ class PlatformOrderController extends Controller
 
     private function refundTotalForOrder(PlatformOrder $order): float
     {
-        // 优先读扁平字段 refund_summary.total_amount
-        $total = data_get($order->meta, 'refund_summary.total_amount');
-        if ($total !== null) {
-            return (float) $total;
-        }
-
-        // 回退：遍历 refund_receipts[].amount
-        $refunds = (array) (data_get($order->meta, 'refund_receipts', []) ?? []);
-        $sum = 0.0;
-        foreach ($refunds as $r) {
-            $sum += (float) (data_get($r, 'amount') ?? 0);
-        }
-
-        return $sum;
+        // 口径统一：集中到模型方法，避免多处复制导致漂移
+        return (float) $order->refundTotal();
     }
 
     protected function sumReceiptAmount($orders): float