Home: watch-time heatmap in the stats area

- extract the 365d fetch+render into heatSection() so ?stats and the
  home stats widget share it (no duplicated async loader)
- home order: stats cards + top 3 -> watch-time heatmap (past year,
  month labels, scrollable) -> history widget

static/app.js

@@ -185,6 +185,8 @@ function showHome() {
     const ta = topAnime(d, 3);
     if (ta) sw.append(ta);
   }).catch(() => load.remove());
+  // 5b. watch-time heatmap (past year, shared with ?stats)
+  main.append(heatSection());
   // 6. history widget (data already loaded, capped at 6)
   const hh = el("div", "sec-head");
   hh.append(el("h2", null, "History"), link(`all ${history.length} \u2192`, "?history"));
@@ -531,24 +533,29 @@ function heatMap(byDay, days) {
   return [lbl, grid, lg];
 }
 
+function heatSection() {
+  const sec = el("section", null);
+  const h = el("div", "sec-head");
+  h.append(el("h2", null, "Watch time by day"), el("span", "muted", "past year"));
+  const load = el("p", "muted", "loading\u2026");
+  sec.append(h, load);
+  api("/api/stats?days=365").then(d2 => {
+    load.remove();
+    const [l, g, leg] = heatMap(d2.by_day, 365);
+    const w = el("div", "heat-wrap");
+    w.append(l, g);
+    sec.append(w, leg);
+  }).catch(() => load.remove());
+  return sec;
+}
+
 async function showStats() {
   skel(5);
   const d = await api("/api/stats?days=30");
   main.innerHTML = "";
   main.append(el("h2", null, "Stats \u2014 last 30 days"));
   main.append(statsCards(d));
-  const hm = el("section", null);
-  const hmh = el("div", "sec-head");
-  hmh.append(el("h2", null, "Watch time by day"), el("span", "muted", "past year"));
-  hm.append(hmh, el("p", "muted", "loading\u2026"));
-  main.append(hm);
-  api("/api/stats?days=365").then(d2 => {
-    hm.querySelector("p.muted")?.remove();
-    const [l, g, leg] = heatMap(d2.by_day, 365);
-    const w = el("div", "heat-wrap");
-    w.append(l, g);
-    hm.append(w, leg);
-  }).catch(() => hm.querySelector("p.muted")?.remove());
+  main.append(heatSection());
   const ta = topAnime(d);
   if (ta) main.append(ta);
   if (d.top_searches.length) {