fix: 修改订单计算逻辑

src/store/modules/carts.ts

@@ -231,9 +231,13 @@ export const useCartsStore = defineStore("carts", () => {
     return [];
   });
 
+  const coupons = ref<BackendCoupon[]>([]);
+  function setCoupons(cps: BackendCoupon[]) {
+    coupons.value = cps;
+  }
   // 优惠券列表
   const backendCoupons = computed<BackendCoupon[]>(() => {
-    return [];
+    return coupons.value;
   });
 
   // 商品加入购物车顺序
@@ -759,7 +763,8 @@ export const useCartsStore = defineStore("carts", () => {
     clearMerchantReduction,
     seatFeeConfig,
     pointDeductionRule,
-    userPoints
+    userPoints,
+    setCoupons
   };
 });