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/rankings.js

@@ -179,6 +179,12 @@ function durationNote(data) {
   return `<div class="section-note">内容效率与互动效率：时长 ≥ ${filter.min_duration_seconds} 秒、发布满 ${filter.maturity_days} 天、播放 ≥ ${filter.min_view}${shrink}；时长缺失不参与。</div>`;
 }
 
+function growthNote(sort, growthDays) {
+  if (sort !== "growth" && sort !== "growth_rate") return "";
+  if (Number(growthDays) !== 1) return "";
+  return `<div class="section-note">近 1 日：当日发布按 0 起算；更早发布的新入库按入库时播放量起算，需要当天至少两次采样。</div>`;
+}
+
 function bindControls(root) {
   root.querySelector("#rank-sort")?.addEventListener("change", (event) => {
     replaceQuery({ sort: event.target.value, page: null });
@@ -245,6 +251,7 @@ async function renderScope(root, { query }, scope) {
     </header>
     ${controls({ scope, sort, within, year, growthDays, q, years })}
     ${durationNote(data)}
+    ${growthNote(sort, growthDays)}
     ${data.available === false ? `<div class="notice-row warning">
       <strong>${sort.startsWith("growth") ? "增长数据尚不可用" : "榜单筛选后为空"}</strong>
       <span>${escapeHtml(data.reason || "")}</span>