ui: no-store cache headers, synopsis below episode grid

- no-store on everything except /stream: stale cached app.js (old CDN
  hls.js ref) was the cause of the black screen — video plays fine in a
  real Chromium once the fresh JS loads (verified via playwright)
- synopsis moved under the episode grid

static/app.js

@@ -79,7 +79,7 @@ async function showAnime(slug_id, opts = {}) {
   main.innerHTML = "";
 
   const head = el("section", "detail-head");
-  head.append(el("h2", null, detail.name), el("p", "synopsis", detail.synopsis || ""));
+  head.append(el("h2", null, detail.name));
   main.append(head);
 
   const player = el("div", "player");
@@ -127,6 +127,8 @@ async function showAnime(slug_id, opts = {}) {
     const cur = [...eps.children].find(b => +b.dataset.ep === opts.ep);
     if (cur) { markActive(cur); play(opts.ep, cur.dataset.no); }
   }
+
+  if (detail.synopsis) main.append(el("p", "synopsis bottom", detail.synopsis));
 }
 
 function langLabel() { return lang === "eng" ? "▶ dub" : "▶ sub"; }