feat: 添加课程详情页的收藏功能

在课程详情页中添加收藏按钮，点击按钮可以切换收藏状态。按钮的图标颜色会根据收藏状态动态变化

@@ -219,13 +219,13 @@
             </svg>
             分享
           </button> -->
-          <button class="flex flex-col items-center text-gray-500 text-xs">
+          <button class="flex flex-col items-center text-gray-500 text-xs" @click="toggleFavorite">
             <svg
               xmlns="http://www.w3.org/2000/svg"
               class="h-6 w-6"
-              fill="none"
+              :fill="isFavorite ? 'red' : 'none'"
               viewBox="0 0 24 24"
-              stroke="currentColor"
+              :stroke="isFavorite ? 'red' : 'currentColor'"
             >
               <path
                 stroke-linecap="round"
@@ -271,8 +271,15 @@ const route = useRoute()
 const router = useRouter()
 const course = ref(null)
 const activeTab = ref('课程特色')
+const isFavorite = ref(false)
 const { addToCart, proceedToCheckout } = useCart()
 
+// Handle favorite toggle
+const toggleFavorite = () => {
+  isFavorite.value = !isFavorite.value
+  // TODO: 后续对接收藏接口
+}
+
 // Curriculum items
 const curriculumItems = [
   { title: '课程特色', active: true },