feat(growth): same-day 1-day baselines for new videos

Let 1-day view growth use a zero baseline for videos published today, and the first successful sample for older videos ingested today, without mixing those into 7/30-day rankings.

reaction_board/web/static/views/home.js

@@ -69,7 +69,7 @@ export async function renderHome(root) {
   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。"
+    ? "当日发布按 0 起算；更早发布的新入库需要当天至少两次采样。"
     : `需要至少 ${growthDays + 1} 天快照才能计算近 ${growthDays} 日增长。`;
   const updatedLabel = formatClock(overview.updated_at);
   const dataDateLabel = formatDataDate(overview.data_date);