feat: home growth auto(7→1) and hourly recent-video snapshot

- Add analytics.home_growth_days (auto|1|7); API growth_days=auto tries 7 then 1
- Homepage shows active window and growth-board link; clearer empty reason
- New snapshot_recent scheduler task (schedule.recent_snapshot_minutes/days)
- run_recent_videos refreshes new aids only; never touches completed/backup
- Full 00:01 job keeps ok=1 skip (covers hourly refresh within 1h); mutex with recent

reaction_board/web/static/views/home.js

@@ -47,7 +47,8 @@ export async function renderHome(root) {
     api("/api/overview"),
     api("/api/videos", { sort: "published", within_days: 14, limit: 6 }),
     api("/api/videos", { sort: "heat", limit: 6 }),
-    api("/api/videos", { sort: "growth", growth_days: 7, limit: 6 }),
+    // auto：服务端按 analytics.home_growth_days 解析；默认先试 7 天再降到 1 天
+    api("/api/videos", { sort: "growth", growth_days: "auto", limit: 6 }),
   ]);
 
   const fans = overview.fans;
@@ -59,6 +60,13 @@ export async function renderHome(root) {
   const pending = overview.counts?.candidates_pending || 0;
   // 候选提示仅对已登录（或未启用鉴权）用户可见，访客不展示运行期信息。
   const showCandidates = pending > 0 && canAccessProtected();
+  const growthDays = Number(growth.growth_days) || 1;
+  const growthLabel = `近 ${growthDays} 日`;
+  const growthEmptyTitle = growth.reason
+    || `近 ${growthDays} 日增长暂不可用`;
+  const growthEmptyHint = growthDays <= 1
+    ? "当前快照不足，完成至少 2 天快照后即可显示播放增量。"
+    : `需要至少 ${growthDays + 1} 天快照才能计算近 ${growthDays} 日增长。`;
 
   root.innerHTML = `<section class="page home-page">
     <header class="page-head home-head">
@@ -101,12 +109,12 @@ export async function renderHome(root) {
 
     <section class="panel">
       <div class="section-head">
-        <h2>增长动态</h2>
-        <a class="text-link" href="/videos?sort=growth&growth_days=7">增长榜</a>
+        <h2>增长动态 · ${escapeHtml(growthLabel)}</h2>
+        <a class="text-link" href="/videos?sort=growth&growth_days=${growthDays}">增长榜</a>
       </div>
       ${growth.available && growth.items.length
         ? `<div class="media-grid">${growth.items.map((item, index) => growthCard(item, index)).join("")}</div>`
-        : emptyState("需要至少 2 天快照", growth.reason || "当前只有 1 个数据点，明天开始显示播放增量。")}
+        : emptyState(growthEmptyTitle, growthEmptyHint)}
     </section>
 
     <section class="panel">