feat(课程详情页): 添加未登录用户购买课程时的登录检查

在立即购买操作前检查用户是否登录，未登录则跳转至登录页并提示

@@ -213,6 +213,7 @@
 import { ref, onMounted, defineComponent, h } from 'vue'
 import { useRoute, useRouter } from 'vue-router'
 import { useCart } from '@/contexts/cart'
+import { useAuth } from '@/contexts/auth'
 import { useTitle } from '@vueuse/core';
 import { showToast } from 'vant';
 import { formatDate } from '@/utils/tools'
@@ -230,6 +231,7 @@ useTitle($route.meta.title);
 
 const route = useRoute()
 const router = useRouter()
+const { currentUser } = useAuth()
 
 const course = ref(null)
 const lecturers = ref([])
@@ -311,6 +313,13 @@ const rightContent = h(RightContent)
 
 // 立即购买操作
 const handlePurchase = () => {
+  // 检查用户是否已登录
+  if (!currentUser.value) {
+    showToast('请先登录')
+    router.replace({ path: '/login', query: { redirect: $route.fullPath } })
+    return
+  }
+
   if (course.value) {
     addToCart({
       id: course.value.id,