refactor(discount): 简化会员折扣空值处理逻辑

- 使用Elvis操作符替代条件表达式判断空值
- 统一两个位置的折扣计算逻辑实现方式
- 提高代码可读性和简洁性

app/src/main/java/com/sw/dualscreen/activity/PayActivity.kt

@@ -196,7 +196,7 @@ class PayActivity : BaseActivity<ActivityPayBinding>() {
             //val onePrice = if (isVip) foodInfo?.vipPrice else foodInfo?.specPrice
             if (isVip) {
                 userViewModel.getMemberDiscount(memberInfo?.faceUserId?:"") { discount ->
-                    memberDiscount = if (discount == null) 1.0 else discount / 10
+                    memberDiscount = discount ?: 1.0
                     var onePrice = foodInfo?.specPrice ?: 0.0
                     onePrice = if (isVip) onePrice * memberDiscount else onePrice
                     it.totalPrice = onePrice * eatNum

app/src/main/java/com/sw/dualscreen/presentation/MainScreenPresentation.kt

@@ -1034,7 +1034,7 @@ class MainScreenPresentation(
 //                pauseCamera()
                 //先查询会员折扣
                 userViewModel.getMemberDiscount(userId) { discount ->
-                    memberDiscount = if (discount == null) 1.0 else discount / 10
+                    memberDiscount = discount ?: 1.0
                     step3ShowRecognizeResult(userId)
                 }
             })