feat(CourseDetailPage): 添加课程封面图片并调整布局

将课程封面图片移至页面顶部，移除重复的图片显示
调整标题区域的圆角样式，优化页面布局

 <template>
-  <AppLayout :rightContent="rightContent">
+  <AppLayout :rightContent="rightContent" :has-title="false">
     <div class="pb-24">
+      <!-- Course Image -->
+      <div class="mb-4">
+        <img :src="course?.cover || 'https://cdn.ipadbiz.cn/mlaj/images/default_block.png'" :alt="course?.title"
+          class="w-full h-auto" />
+      </div>
+
       <!-- Course Header -->
       <div class="px-4">
-        <div class="bg-gradient-to-b from-red-500 to-red-600 p-4 mb-4 rounded-b-3xl shadow-lg">
+        <div class="bg-gradient-to-b from-red-500 to-red-600 p-4 mb-4 rounded-xl shadow-lg">
           <div v-if="course?.group_type_title" class="bg-white/10 backdrop-blur-sm rounded-lg p-3 mb-3 inline-block">
             <div class="text-white font-semibold">{{ course?.group_type_title }}</div>
           </div>
@@ -33,12 +39,6 @@
           <p v-html="course?.introduce" class="text-gray-700 whitespace-pre-line"></p>
         </FrostedGlass>
 
-        <!-- Course Image -->
-        <div class="mb-6">
-          <img :src="course?.cover || 'https://cdn.ipadbiz.cn/mlaj/images/default_block.png'" :alt="course?.title"
-            class="w-full h-auto rounded-xl shadow-md" />
-        </div>
-
         <!-- Tab Navigation -->
         <FrostedGlass class="mb-6 rounded-xl overflow-hidden">
           <div class="border-b border-gray-200">