fix: 修复游客购物车商品显示和添加地址问题

- ProductDetail.vue: 添加购物车时传入完整商品信息
- Cart.vue: 未登录点击添加地址跳转登录页
- 游客购物车正确显示商品状态

frontend/src/views/user/Cart.vue

@@ -158,9 +158,9 @@
           </div>
           <div class="no-address" v-else>
             <p>您还没有添加收货地址</p>
-            <el-button type="primary" @click="showAddAddress = true">添加地址</el-button>
+            <el-button type="primary" @click="handleAddAddressClick">添加地址</el-button>
           </div>
-          <el-button class="add-address-btn" link type="primary" @click="showAddAddress = true" v-if="addresses.length">
+          <el-button class="add-address-btn" link type="primary" @click="handleAddAddressClick" v-if="addresses.length">
             <el-icon><Plus /></el-icon>
             添加新地址
           </el-button>
@@ -498,6 +498,16 @@ async function fetchAddresses() {
   } catch {}
 }
 
+// 点击添加地址按钮
+function handleAddAddressClick() {
+  if (!cartStore.isLoggedIn()) {
+    ElMessage.warning('请先登录后再添加地址')
+    router.push('/login')
+    return
+  }
+  showAddAddress.value = true
+}
+
 async function addAddress() {
   if (!addressForm.name || !addressForm.phone || !addressForm.address) {
     ElMessage.warning('请填写必要信息')

frontend/src/views/user/ProductDetail.vue

@@ -124,7 +124,8 @@ async function addToCart() {
   }
 
   try {
-    await cartStore.addItem(product.value.id, quantity.value)
+    // 传入商品信息，支持游客购物车显示
+    await cartStore.addItem(product.value.id, quantity.value, product.value)
     ElMessage.success(t('product.addToCart') + ' ✓')
   } catch (err: any) {
     // 处理后端返回的错误