feat: remove tax fee from checkout summary

frontend/src/views/admin/Settings.vue

@@ -6,7 +6,6 @@
           <el-form :model="settings" label-width="160px">
             <el-form-item label="渠道费率 (%)"><el-input-number v-model="settings.payment_channel_fee_rate" :precision="2" /></el-form-item>
             <el-form-item label="服务费率 (%)"><el-input-number v-model="settings.service_fee_rate" :precision="2" /></el-form-item>
-            <el-form-item label="税费 (%)"><el-input-number v-model="settings.tax_rate" :precision="2" /></el-form-item>
             <el-form-item label="包装费 (元)"><el-input-number v-model="settings.packaging_fee" :precision="2" :min="0" /></el-form-item>
             <el-form-item label="国际计算手续费 (%)"><el-input-number v-model="settings.international_fee_rate" :precision="2" :min="0" /></el-form-item>
             <el-form-item label="邀请奖励积分"><el-input-number v-model="settings.invite_credit_reward" /></el-form-item>
@@ -37,7 +36,6 @@ import { adminApi } from '../../api'
 const settings = reactive<Record<string, any>>({
   payment_channel_fee_rate: 0,
   service_fee_rate: 0,
-  tax_rate: 0,
   packaging_fee: 0,
   international_fee_rate: 0,
   invite_credit_reward: 0

frontend/src/views/user/Cart.vue

@@ -205,11 +205,6 @@
           <span>服务费 ({{ settings.service_fee_rate || 0 }}%)</span>
           <span>¥{{ serviceFee.toFixed(2) }}</span>
         </div>
-        
-        <div class="summary-row" v-if="taxFee > 0">
-          <span>税费 ({{ settings.tax_rate || 0 }}%)</span>
-          <span>¥{{ taxFee.toFixed(2) }}</span>
-        </div>
 
         <div class="summary-row" v-if="channelFee > 0">
           <span>通道费 ({{ settings.payment_channel_fee_rate || 0 }}%)</span>
@@ -435,11 +430,6 @@ const serviceFee = computed(() => {
   return selectedTotal.value * rate / 100
 })
 
-const taxFee = computed(() => {
-  const rate = parseFloat(settings.value.tax_rate || '0')
-  return selectedTotal.value * rate / 100
-})
-
 const channelFee = computed(() => {
   const rate = parseFloat(settings.value.payment_channel_fee_rate || '0')
   return selectedTotal.value * rate / 100
@@ -455,7 +445,7 @@ const internationalFee = computed(() => {
 })
 
 const grandTotal = computed(() => {
-  return selectedTotal.value + shippingFee.value + serviceFee.value + taxFee.value + channelFee.value + packagingFee.value + internationalFee.value
+  return selectedTotal.value + shippingFee.value + serviceFee.value + channelFee.value + packagingFee.value + internationalFee.value
 })
 
 const canCheckout = computed(() => {