style,refactor,feat: 统一卡片布局为图片在上并优化细节

1. 调整全局默认卡片样式为image_top，更新各页面默认布局配置
2. 给文章卡片添加variant属性适配双列/单列布局
3. 优化文章内容区域文字样式与评论列表空状态
4. 简化快捷导航组件代码，移除冗余样式与多余props
5. 优化markdown渲染配置与评论头像空格格式

src/pages/tabbar/home/home.vue

@@ -249,7 +249,7 @@
 			<view class="box-border p-3 pt-0"
 				:class="homeListLayout === 'double' ? 'grid grid-cols-2 gap-3' : 'flex flex-col gap-y-3'">
 				<uh-article-card v-for="(article, index) in articleList" :key="index" from="home" :article="article"
-					:audit-mode="calcAuditModeEnabled" />
+					:variant="homeListLayout === 'double' ? 'grid' : 'list'" :audit-mode="calcAuditModeEnabled" />
 			</view>
 			<view class="mt-3 box-border pb-5 text-center text-xs text-gray-400">
 				{{ loadMoreText }}