fix(web): fix UP card layout and fan delta semantics

reaction_board/web/static/views/up.js

@@ -35,7 +35,7 @@ export async function renderUp(root, { params, query }) {
 
   root.innerHTML = `<section class="page up-page">
     <header class="page-head">
-      <a class="back-link" href="#/rank?scope=up&sort=views">← 返回 UP 榜</a>
+      <a class="back-link" href="#/rank?scope=up&sort=avg_views">← 返回 UP 榜</a>
       <a class="button ghost" href="${escapeAttr(up.space_url)}" target="_blank" rel="noreferrer">B 站空间</a>
     </header>
 
@@ -65,10 +65,10 @@ export async function renderUp(root, { params, query }) {
       <p class="section-note">按该 UP 全部视频的每日播放合计绘制；缺失日期断开。</p>
     </section>
 
-    <section class="panel chart-panel">
+    ${videos.length > 1 ? `<section class="panel chart-panel">
       ${sectionHeader("单视频播放对比")}
       ${topForBar.length ? `<div class="chart chart-tall" id="up-bars"></div>` : emptyState("暂无视频数据")}
-    </section>
+    </section>` : ""}
 
     <section class="panel">
       <div class="section-head">