style(StudyDetailPage): 调整学习资料入口的样式和颜色

将背景色改为绿色，图标改为白色，并添加阴影效果以提升视觉层次感

@@ -98,12 +98,12 @@
 
                     <!-- 学习资料入口 -->
                     <div v-if="course.course_type === 'file' && courseFile?.list && courseFile.list.length > 0"
-                        class="bg-white rounded-lg p-4 mb-4 cursor-pointer hover:bg-gray-50 transition-colors mt-4"
+                        class="bg-white rounded-lg p-4 mb-4 cursor-pointer hover:bg-gray-50 transition-colors mt-4 shadow-sm"
                         @click="showMaterialsPopup = true">
                         <div class="flex items-center justify-between">
                             <div class="flex items-center gap-3">
-                                <div class="w-10 h-10 bg-blue-100 rounded-lg flex items-center justify-center">
-                                    <van-icon name="notes" class="text-green-600" size="20" />
+                                <div class="w-10 h-10 bg-green-600 rounded-lg flex items-center justify-center">
+                                    <van-icon name="notes" class="text-white" size="20" />
                                 </div>
                                 <div>
                                     <div class="text-base font-medium text-gray-900">学习资料</div>