Episode names: render MAL titles on the episode grid

anidb's episodes API has no names (id/number/filler only), but the
Jikan call we already make for intro timings carries them (title +
title_japanese). _parse_intros now keeps one entry per episode with
title and optional start/length (entries are never null anymore).

Client: attachEpNames() reuses the introCache promise, stamps
epsList[i].name, re-renders; buttons show the name (3-line clamp) +
full tooltip. Jikan down => no names, no error (same graceful
degradation as the skip-intro button).

Verified headless: Jujutsu Kaisen S1 24/24 buttons named
('E1 | Ryomen Sukuna' ...); S2 (Jikan 504 at the time) rendered
gracefully without names. 17/17 API tests.

server/upstream.py

@@ -141,12 +141,15 @@ def _languages(ep_id):
 
 
 def _parse_intros(eps):
-    """Jikan episode list -> [{start, length}, ...], None where MAL has no timing"""
+    """Jikan episode list -> one entry per episode: {title?, start?, length?}.
+    title from MAL (episode name); start/length only when MAL has the timing."""
     out = []
     for e in eps:
         i = e.get("intro") or {}
-        out.append({"start": int(i["start"]), "length": int(i["length"])}
-                   if i.get("start") is not None else None)
+        d = {"title": e.get("title") or None}
+        if i.get("start") is not None:
+            d.update(start=int(i["start"]), length=int(i["length"]))
+        out.append(d)
     return out