fix(order): calculate invitation commission after balance deduction (#1020)

Calculate invitation commission from the amount remaining after balance deductions, preventing duplicate commission on internally credited payments.

app/Services/OrderService.php

@@ -74,12 +74,14 @@ class OrderService
 
             $orderService->setVipDiscount($user);
             $orderService->setOrderType($user);
-            $orderService->setInvite(user: $user);
 
             if ($user->balance && $order->total_amount > 0) {
                 $orderService->handleUserBalance($user, $userService);
             }
 
+            // 余额抵扣后的 total_amount 才是用户实际支付金额，返利必须基于该金额计算。
+            $orderService->setInvite(user: $user);
+
             if (!$order->save()) {
                 throw new ApiException(__('Failed to create order'));
             }