feat: 商品添加克重字段,订单添加通道费,运费按重量计算

- 商品模型: 添加weight字段(克重)
- 订单模型: 添加channel_fee字段(支付通道费)
- 后台商品管理: 添加克重输入框
- 后台订单详情: 显示通道费
- 订单创建: 根据商品重量计算运费,添加通道费计算
- 购物车: 根据商品重量计算运费,显示通道费

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/admin/Orders.vue

@@ -104,6 +104,10 @@
               <span>税费</span>
               <span>¥{{ (currentOrder.tax || 0).toFixed(2) }}</span>
             </div>
+            <div class="fee-item" v-if="currentOrder.channel_fee > 0">
+              <span>通道费</span>
+              <span>¥{{ (currentOrder.channel_fee || 0).toFixed(2) }}</span>
+            </div>
             <div class="fee-item total">
               <span>合计</span>
               <span class="total-amount">¥{{ (currentOrder.total_amount || 0).toFixed(2) }}</span>

frontend/src/views/admin/Products.vue

@@ -80,17 +80,22 @@
         <div class="form-section">
           <div class="section-title">价格库存</div>
           <el-row :gutter="16">
-            <el-col :span="8">
+            <el-col :span="6">
               <el-form-item label="价格" required>
                 <el-input-number v-model="form.price" :precision="2" :min="0" style="width: 100%" />
               </el-form-item>
             </el-col>
-            <el-col :span="8">
+            <el-col :span="6">
               <el-form-item label="库存">
                 <el-input-number v-model="form.stock" :min="0" style="width: 100%" />
               </el-form-item>
             </el-col>
-            <el-col :span="8">
+            <el-col :span="6">
+              <el-form-item label="克重(克)">
+                <el-input-number v-model="form.weight" :precision="1" :min="0" style="width: 100%" />
+              </el-form-item>
+            </el-col>
+            <el-col :span="6">
               <el-form-item label="上架">
                 <el-switch v-model="form.is_active" />
               </el-form-item>
@@ -188,6 +193,7 @@ const form = reactive({
   name: '',
   description: '',
   price: 0,
+  weight: 0,
   stock: 0,
   min_purchase: 1,
   max_purchase: undefined as number | undefined,
@@ -264,11 +270,11 @@ async function fetchBrands() {
 
 function openAdd() {
   editing.value = null
-  Object.assign(form, { 
-    name: '', description: '', price: 0, stock: 0, 
-    min_purchase: 1, max_purchase: undefined, 
-    require_credit: false, credit_cost: 0, credit_reward: 0, 
-    is_active: true, category_ids: [], brand_id: undefined 
+  Object.assign(form, {
+    name: '', description: '', price: 0, weight: 0, stock: 0,
+    min_purchase: 1, max_purchase: undefined,
+    require_credit: false, credit_cost: 0, credit_reward: 0,
+    is_active: true, category_ids: [], brand_id: undefined
   })
   fileList.value = []
   uploadedUrls.value = []
@@ -281,6 +287,7 @@ function editProd(row: any) {
     name: row.name,
     description: row.description || '',
     price: row.price,
+    weight: row.weight || 0,
     stock: row.stock || 0,
     min_purchase: row.min_purchase || 1,
     max_purchase: row.max_purchase,

frontend/src/views/user/Cart.vue

@@ -209,7 +209,12 @@
           <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>
+          <span>¥{{ channelFee.toFixed(2) }}</span>
+        </div>
+
         <div class="summary-divider"></div>
         
         <div class="summary-row summary-total">
@@ -334,11 +339,18 @@ const selectedQuantity = computed(() => {
     .reduce((sum, item) => sum + item.quantity, 0)
 })
 
+// 计算选中商品的总重量
+const selectedWeight = computed(() => {
+  return items.value
+    .filter(item => selectedIds.value.includes(item.id))
+    .reduce((sum, item) => sum + (item.product?.weight || 0) * item.quantity, 0)
+})
+
 const shippingFee = computed(() => {
   const firstWeight = parseFloat(settings.value.shipping_fee_first_weight || '0')
   const perGram = parseFloat(settings.value.shipping_fee_per_gram || '0')
   if (selectedTotal.value >= 99 || firstWeight === 0) return 0
-  return firstWeight + perGram * Math.max(0, selectedQuantity.value - 500)
+  return firstWeight + perGram * Math.max(0, selectedWeight.value - 500)
 })
 
 const serviceFee = computed(() => {
@@ -351,8 +363,13 @@ const taxFee = computed(() => {
   return selectedTotal.value * rate / 100
 })
 
+const channelFee = computed(() => {
+  const rate = parseFloat(settings.value.payment_channel_fee_rate || '0')
+  return selectedTotal.value * rate / 100
+})
+
 const grandTotal = computed(() => {
-  return selectedTotal.value + shippingFee.value + serviceFee.value + taxFee.value
+  return selectedTotal.value + shippingFee.value + serviceFee.value + taxFee.value + channelFee.value
 })
 
 const canCheckout = computed(() => {