feat(platform-orders): 退款总额统计（详情页+导出）

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

@@ -24,6 +24,13 @@
         <tr><th>支付时间</th><td>{{ optional($order->paid_at)->format('Y-m-d H:i:s') ?: '-' }}</td></tr>
         <tr><th>生效时间</th><td>{{ optional($order->activated_at)->format('Y-m-d H:i:s') ?: '-' }}</td></tr>
         <tr><th>退款时间</th><td>{{ optional($order->refunded_at)->format('Y-m-d H:i:s') ?: '-' }}</td></tr>
+        @php
+            $refundTotal = 0.0;
+            foreach ((array) (data_get($order->meta, 'refund_receipts', []) ?? []) as $r) {
+                $refundTotal += (float) (data_get($r, 'amount') ?? 0);
+            }
+        @endphp
+        <tr><th>退款总额</th><td>¥{{ number_format($refundTotal, 2) }}</td></tr>
         </tbody>
     </table>