feat: add packaging fee and international fee to checkout summary

frontend/src/views/admin/Settings.vue

@@ -7,6 +7,8 @@
             <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>
             <el-form-item label="验证码功能"><el-switch v-model="verifyEnabled" active-value="true" inactive-value="false" /></el-form-item>
             <el-form-item><el-button type="primary" @click="saveSettings">保存</el-button></el-form-item>
@@ -36,6 +38,8 @@ 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
 })
 const verifyEnabled = ref('true')

frontend/src/views/user/Cart.vue

@@ -216,6 +216,16 @@
           <span>¥{{ channelFee.toFixed(2) }}</span>
         </div>
 
+        <div class="summary-row" v-if="packagingFee > 0">
+          <span>包装费</span>
+          <span>¥{{ packagingFee.toFixed(2) }}</span>
+        </div>
+
+        <div class="summary-row" v-if="internationalFee > 0">
+          <span>国际计算手续费 ({{ settings.international_fee_rate || 0 }}%)</span>
+          <span>¥{{ internationalFee.toFixed(2) }}</span>
+        </div>
+
         <div class="summary-divider"></div>
         
         <div class="summary-row summary-total">
@@ -435,8 +445,17 @@ const channelFee = computed(() => {
   return selectedTotal.value * rate / 100
 })
 
+const packagingFee = computed(() => {
+  return parseFloat(settings.value.packaging_fee || '0')
+})
+
+const internationalFee = computed(() => {
+  const rate = parseFloat(settings.value.international_fee_rate || '0')
+  return selectedTotal.value * rate / 100
+})
+
 const grandTotal = computed(() => {
-  return selectedTotal.value + shippingFee.value + serviceFee.value + taxFee.value + channelFee.value
+  return selectedTotal.value + shippingFee.value + serviceFee.value + taxFee.value + channelFee.value + packagingFee.value + internationalFee.value
 })
 
 const canCheckout = computed(() => {