fix: 不选择用户后清除优惠券，修改优惠券可用数量计算公式为数量-退菜-退款

src/views/tool/Instead/components/order.vue

@@ -346,6 +346,7 @@ const seatAmount = computed(() => {
 watch(
   () => props.user.id,
   (newval) => {
+    quansSelArr.value = [];
     if (newval !== "") {
       pointsInit();
     }

src/views/tool/Instead/quan_util.js

@@ -31,7 +31,7 @@ export function returnCoupCanUse(goodsArr = [], coup, selCoupArr = []) {
     return false;
   }
   const findGoodsTotalNumber = findGoods.reduce((prve, cur) => {
-    const num = cur.num - cur.refundNum;
+    const num = cur.num - cur.refundNum - cur.returnNum;
     return prve + (num <= 0 ? 0 : num);
   }, 0);
   const selCoupNumber = selCoupArr