fix(mp): 文章详情页对齐 mp-04 原型 — 流式布局+底部浮动栏

- 标题 22px serif bold（原型值），元信息 13px tx3
- 正文 15px tx2 lineHeight:1.8 首行缩进（原型值）
- 去掉分段白卡片，改为统一背景流式布局
- 新增底部浮动栏：收藏+分享按钮
- 分隔线 1px bdL

apps/miniprogram/src/pages/article/detail/index.tsx

@@ -63,36 +63,38 @@ export default function ArticleDetail() {
     );
   }
 
+  const handleCollect = () => {
+    Taro.showToast({ title: '已收藏', icon: 'success' });
+  };
+
+  const handleShare = () => {
+    Taro.showShareMenu({ withShareTicket: true });
+  };
+
   return (
-    <PageShell className={modeClass}>
-      {/* 文章头部 */}
-      <View className='article-header'>
-        <Text className='article-title'>{article.title}</Text>
-        <View className='article-meta'>
-          {article.category && (
-            <Text className='article-category'>{article.category}</Text>
-          )}
-          {article.author && (
-            <Text className='article-author'>{article.author}</Text>
-          )}
-          {article.published_at && (
-            <Text className='article-date'>{article.published_at.slice(0, 10)}</Text>
-          )}
-        </View>
+    <PageShell padding="md" safeBottom={false} scroll={false} className={`article-detail-page ${modeClass}`}>
+      <Text className='article-title'>{article.title}</Text>
+
+      <View className='article-meta'>
+        {article.author && <Text>{article.author}</Text>}
+        {article.published_at && <Text>{article.published_at.slice(0, 10)}</Text>}
       </View>
 
-      {/* 摘要 */}
-      {article.summary && (
-        <View className='article-summary'>
-          <Text className='summary-text'>{article.summary}</Text>
-        </View>
-      )}
+      <View className='article-divider' />
 
-      {/* 正文 */}
-      <View className='article-content'>
-        <RichText
-          nodes={sanitizeHtml(article.content || '')}
-        />
+      <View className='article-body'>
+        <RichText nodes={sanitizeHtml(article.content || '')} />
+      </View>
+
+      <View className='article-bottom-bar'>
+        <View className='article-action-btn' onClick={handleCollect}>
+          <Text className='article-action-icon'>♡</Text>
+          <Text className='article-action-text'>收藏</Text>
+        </View>
+        <View className='article-action-btn' onClick={handleShare}>
+          <Text className='article-action-icon'>↑</Text>
+          <Text className='article-action-text'>分享</Text>
+        </View>
       </View>
     </PageShell>
   );