fix(system): three next-runs, completed-date data_date, running mark

Split /system schedule into fans / snapshot+UP / discovery next-runs.
Drive data_date and snapshot_days from fully completed video snapshots
only, keep prior success date on failure, show task failure records, and
mark in-progress tasks as 运行中 without wall-clock next-run jumps.

reaction_board/web/static/views/system.js

@@ -93,11 +93,11 @@ export async function renderSystem(root) {
     <section class="panel">
       ${sectionHeader("预计下次运行")}
       <div class="status-grid status-row-3">
-        <div><span>搜索发现</span><strong>${escapeHtml(formatDateTime(next.discover))}</strong></div>
-        <div><span>每日快照</span><strong>${escapeHtml(formatDateTime(next.snapshot))}</strong></div>
-        <div><span>发现周期</span><strong>${system.schedule.discover_minutes} 分钟</strong></div>
+        <div><span>咻咻满粉丝数更新</span><strong>${running.fans ? "运行中" : escapeHtml(formatDateTime(next.fans))}</strong></div>
+        <div><span>视频数据快照 + UP 信息</span><strong>${running.snapshot ? "运行中" : escapeHtml(formatDateTime(next.snapshot))}</strong></div>
+        <div><span>新视频搜索</span><strong>${running.discover || running.discovery ? "运行中" : escapeHtml(formatDateTime(next.discover))}</strong></div>
       </div>
-      <p class="section-note">预计时间按配置和最近任务完成时间推算；实际以常驻进程为准。</p>
+      <p class="section-note">进行中显示「运行中」；空闲时按该任务上次完成时间推算下次运行，不按墙钟抢跑。</p>
     </section>
 
     <section class="panel">