fix: 未登录时静默跳过需要认证的API调用

- ProductDetail.vue: fetchUserCredits 添加登录检查
- Cart.vue: fetchUserProfile 添加登录检查
- Lotteries.vue: fetchLotteries 添加登录检查
- LotteryDetail.vue: getById/register 添加登录检查和错误处理

避免未登录用户访问页面时出现401错误

frontend/src/views/user/Cart.vue

@@ -458,10 +458,16 @@ async function fetchSettings() {
 }
 
 async function fetchUserProfile() {
+  // 未登录时静默跳过
+  const token = localStorage.getItem('token')
+  if (!token) return
+  
   try {
     const res: any = await userApi.getProfile()
     userCredits.value = res.data?.purchase_credits || 0
-  } catch {}
+  } catch {
+    // 静默处理错误
+  }
 }
 
 async function fetchPaymentChannels() {

frontend/src/views/user/Lotteries.vue

@@ -36,11 +36,23 @@ function formatDate(date: string) {
 }
 
 async function fetchLotteries() {
+  // 检查是否登录
+  const token = localStorage.getItem('token')
+  if (!token) {
+    loading.value = false
+    return
+  }
+  
+  try {
     loading.value = true
     const res: any = await lotteryApi.list()
     lotteries.value = res.data || []
     total.value = res.pagination?.total || res.data?.length || 0
+  } catch {
+    // 静默处理错误
+  } finally {
     loading.value = false
+  }
 }
 
 onMounted(fetchLotteries)

frontend/src/views/user/LotteryDetail.vue

@@ -46,13 +46,36 @@ function formatDate(date: string) {
 }
 
 onMounted(async () => {
+  // 检查是否登录
+  const token = localStorage.getItem('token')
+  if (!token) {
+    ElMessage.warning('请先登录后再查看抽奖详情')
+    return
+  }
+  
+  try {
     const res: any = await lotteryApi.getById(Number(route.params.id))
     lottery.value = res.data
+  } catch {
+    // 静默处理错误
+  }
 })
 
 async function register() {
+  // 检查是否登录
+  const token = localStorage.getItem('token')
+  if (!token) {
+    ElMessage.warning('请先登录后再报名')
+    return
+  }
+  
+  try {
     await lotteryApi.register(Number(route.params.id))
     ElMessage.success('报名成功')
+  } catch (err: any) {
+    const errorMsg = err.response?.data?.error || '报名失败'
+    ElMessage.error(errorMsg)
+  }
 }
 </script>