feat: 支持游客购物车，下单时才需要登录

- cart.ts: 使用 localStorage 存储游客购物车，登录后合并
- Cart.vue: 下单时检查登录状态
- Login.vue: 登录成功后自动合并游客购物车
- api/index.ts: cart list 使用静默模式避免 401 跳转

游客可以浏览商品、添加购物车，只有下单时才需要登录

frontend/src/api/index.ts

@@ -65,7 +65,7 @@ export const productApi = {
 }
 
 export const cartApi = {
-  list: () => api.get('/cart'),
+  list: () => api.get('/cart', { silent: true } as any),
   add: (data: any) => api.post('/cart', data),
   update: (id: number, data: any) => api.put(`/cart/${id}`, data),
   delete: (id: number) => api.delete(`/cart/${id}`),

frontend/src/store/cart.ts

@@ -2,51 +2,154 @@ import { ref, watch } from 'vue'
 import { defineStore } from 'pinia'
 import { cartApi } from '../api'
 
+const LOCAL_CART_KEY = 'guest_cart'
+
 export const useCartStore = defineStore('cart', () => {
   const items = ref<any[]>([])
   const loading = ref(false)
   const totalAmount = ref(0)
   const totalCount = ref(0)
 
+  // 检查是否登录
+  function isLoggedIn(): boolean {
+    return !!localStorage.getItem('token')
+  }
+
+  // 获取游客购物车
+  function getGuestCart(): any[] {
+    const cartStr = localStorage.getItem(LOCAL_CART_KEY)
+    return cartStr ? JSON.parse(cartStr) : []
+  }
+
+  // 保存游客购物车
+  function saveGuestCart(cart: any[]) {
+    localStorage.setItem(LOCAL_CART_KEY, JSON.stringify(cart))
+  }
+
+  // 获取购物车（登录用户从服务器，游客从本地）
   async function fetchCart() {
     loading.value = true
     try {
+      if (isLoggedIn()) {
+        // 登录用户：从服务器获取
         const res: any = await cartApi.list()
         items.value = res.data || []
+      } else {
+        // 游客：从本地存储获取
+        items.value = getGuestCart()
+      }
+    } catch {
+      // 登录用户API失败时，也尝试使用本地数据
+      items.value = getGuestCart()
     } finally {
       loading.value = false
     }
   }
 
-  async function addItem(productId: number, quantity: number) {
+  // 添加商品到购物车
+  async function addItem(productId: number, quantity: number, product?: any) {
+    if (isLoggedIn()) {
+      // 登录用户：添加到服务器
       await cartApi.add({ product_id: productId, quantity })
       await fetchCart()
+    } else {
+      // 游客：添加到本地
+      const guestCart = getGuestCart()
+      const existingItem = guestCart.find(item => item.product_id === productId)
+      
+      if (existingItem) {
+        existingItem.quantity += quantity
+      } else {
+        guestCart.push({
+          id: Date.now(), // 临时ID
+          product_id: productId,
+          quantity,
+          product: product || null
+        })
       }
       
+      saveGuestCart(guestCart)
+      items.value = guestCart
+    }
+  }
+
+  // 更新购物车项数量
   async function updateItem(id: number, quantity: number) {
+    if (isLoggedIn()) {
       await cartApi.update(id, { quantity })
       await fetchCart()
+    } else {
+      // 游客：更新本地
+      const guestCart = getGuestCart()
+      const item = guestCart.find(item => item.id === id)
+      if (item) {
+        item.quantity = quantity
+        saveGuestCart(guestCart)
+        items.value = guestCart
+      }
+    }
   }
 
+  // 删除购物车项
   async function removeItem(id: number) {
+    if (isLoggedIn()) {
       await cartApi.delete(id)
       await fetchCart()
+    } else {
+      // 游客：从本地删除
+      const guestCart = getGuestCart()
+      const filtered = guestCart.filter(item => item.id !== id)
+      saveGuestCart(filtered)
+      items.value = filtered
+    }
   }
 
+  // 删除多个购物车项
   async function removeItems(ids: number[]) {
+    if (isLoggedIn()) {
       await Promise.all(ids.map(id => cartApi.delete(id)))
       await fetchCart()
+    } else {
+      // 游客：批量删除本地项
+      const guestCart = getGuestCart()
+      const filtered = guestCart.filter(item => !ids.includes(item.id))
+      saveGuestCart(filtered)
+      items.value = filtered
+    }
   }
 
+  // 清空购物车
   function clearCart() {
     items.value = []
     totalAmount.value = 0
     totalCount.value = 0
+    localStorage.removeItem(LOCAL_CART_KEY)
+  }
+
+  // 登录后合并游客购物车到服务器
+  async function mergeGuestCart() {
+    const guestCart = getGuestCart()
+    if (guestCart.length === 0) return
+
+    // 将游客购物车中的商品添加到服务器购物车
+    for (const item of guestCart) {
+      try {
+        await cartApi.add({ product_id: item.product_id, quantity: item.quantity })
+      } catch {
+        // 单个商品添加失败不影响其他商品
+      }
+    }
+
+    // 清空游客购物车
+    localStorage.removeItem(LOCAL_CART_KEY)
+    
+    // 刷新购物车
+    await fetchCart()
   }
 
   function calcTotals() {
-    totalAmount.value = items.value.reduce((sum, item) => sum + (item.product?.price || 0) * item.quantity, 0)
-    totalCount.value = items.value.reduce((sum, item) => sum + item.quantity, 0)
+    totalAmount.value = items.value.reduce((sum: number, item: any) => sum + (item.product?.price || 0) * item.quantity, 0)
+    totalCount.value = items.value.reduce((sum: number, item: any) => sum + item.quantity, 0)
   }
 
   watch(items, calcTotals, { deep: true })
@@ -61,6 +164,8 @@ export const useCartStore = defineStore('cart', () => {
     updateItem,
     removeItem,
     removeItems,
-    clearCart
+    clearCart,
+    mergeGuestCart,
+    isLoggedIn
   }
 })

frontend/src/views/auth/Login.vue

@@ -54,6 +54,12 @@ async function handleLogin() {
   loading.value = true
   try {
     await userStore.login(form)
+    
+    // 登录成功后合并游客购物车
+    const { useCartStore } = await import('../../store/cart')
+    const cartStore = useCartStore()
+    await cartStore.mergeGuestCart()
+    
     ElMessage.success(t('auth.loginSuccess'))
     const user = userStore.user
     if (user?.role === 'admin') router.push('/admin')

frontend/src/views/user/Cart.vue

@@ -2,6 +2,7 @@
   <div class="cart-page">
     <BackNav />
     
+    <!-- 购物车为空 -->
     <el-empty v-if="!items.length" description="购物车是空的" :image-size="120">
       <template #image>
         <el-icon :size="80" color="rgba(255,255,255,0.2)"><ShoppingCart /></el-icon>
@@ -573,6 +574,13 @@ async function removeSelected() {
 }
 
 async function handleCheckout() {
+  // 检查是否登录
+  if (!cartStore.isLoggedIn()) {
+    ElMessage.warning('请先登录后再下单')
+    router.push('/login')
+    return
+  }
+
   if (!canCheckout.value) {
     if (!selectedAddressId.value) {
       ElMessage.warning('请选择收货地址')