fix: 前端优惠金额不能为负数

src/pages/order/create.vue

@@ -278,8 +278,12 @@ export default {
         return sum + (item.price * item.quantity)
       }, 0)
       
-      // 2. 优惠金额直接使用用户输入的值
-      this.discountAmount = parseFloat(this.discountMoney) || 0
+      // 2. 优惠金额直接使用用户输入的值，不能为负
+      let discountVal = parseFloat(this.discountMoney)
+      if (isNaN(discountVal) || discountVal < 0) {
+        discountVal = 0
+      }
+      this.discountAmount = discountVal
       
       // 3. 计算实付金额 = 原价 - 优惠金额
       this.actualAmount = this.totalAmount - this.discountAmount
@@ -302,6 +306,13 @@ export default {
         return
       }
 
+      // 校验：优惠金额不能为负
+      const discountVal = parseFloat(this.discountMoney) || 0
+      if (discountVal < 0) {
+        uni.showToast({ title: '优惠金额不能为负', icon: 'none' })
+        return
+      }
+
       const data = {
         customerId: this.selectedCustomer ? this.selectedCustomer.customerId : null,
         items: this.orderItems.map(item => ({