refactor(CheckoutPage): 调整支付弹窗高度和返回按钮逻辑

将支付弹窗的高度调整为100%，移除不必要的圆角样式。修改支付成功后的返回按钮逻辑，从返回首页改为返回上一页，并更新按钮文本为“完成”。简化代码，移除冗余的导航逻辑。

@@ -251,14 +251,12 @@
     <van-popup
       v-model:show="showPayment"
       position="bottom"
-      round
-      :style="{ height: '50%' }"
+      :style="{ height: '100%' }"
     >
       <div class="bg-gradient-to-r from-green-500/10 to-blue-500/10 h-full">
         <WechatPayment
           v-if="showPayment && orderId"
           :order-id="orderId"
-          cancelBtnText="关闭"
           @success="handlePaymentSuccess"
           @failed="handlePaymentFailed"
           @processing="handlePaymentProcessing"
@@ -266,10 +264,10 @@
         >
           <template #success-action>
             <button
-              @click="handleBackToHome"
+              @click="handleBack"
               class="w-full bg-gradient-to-r from-green-500 to-green-600 text-white py-3 rounded-xl font-medium"
             >
-              返回首页
+              完成
             </button>
           </template>
           <template #failed-action>
@@ -375,8 +373,6 @@ const handleSubmit = async (e) => {
 const handlePaymentSuccess = () => {
   orderComplete.value = true
   clearCart();
-  // 返回上一页
-  router.go(-1)
 }
 
 // 处理支付失败
@@ -390,8 +386,8 @@ const handlePaymentProcessing = () => {
   console.log('支付处理中...')
 }
 
-// Handle navigation back to home after order completion
-const handleBackToHome = () => {
-  router.push('/')
+// 返回详情页
+const handleBack = () => {
+  router.go(-1)
 }
 </script>