fix(plex): Restart only where an episode has a resume point; the Surprise draw is re-read, not redrawn

Show cards carry resumable (ShowState, from the same rollup) so a part-watched
show whose next episode is untouched offers Play, not a Continue and a Restart
that do the same thing; plexStarted is the one rule for cards and menus. The
Surprise rail's key sits under the discover root: whatever refreshes the rails
re-reads the draw (keep=) with its watch state now, kept past the 5-minute gc,
and only the reshuffle deals. Closing the player refreshes the Discover rails.
A show card's play acts on the last click only, and only where it was made.

backend/app/routes/plex/detail.py

@@ -29,7 +29,7 @@ from app.plex import people as plex_people
 from app.plex import rollup, subtitles
 from app.plex.query import title_col
 from app.plex import tmdb as plex_tmdb
-from app.plex.cards import episode_card, movie_card, show_card
+from app.plex.cards import SHOW_NEW, episode_card, movie_card, show_card
 from app.plex.client import PlexClient, PlexError, PlexNotConfigured
 from app.plex.lookups import by_rating_key
 from app.routes.plex._shared import _norm_lang, item_or_404
@@ -279,7 +279,7 @@ def _relatedshow_cards(
         if sh is None or rk in seen:
             continue
         seen.add(rk)
-        out.append(show_card(sh, statuses.get(sh.id, "new"), lang=lang))
+        out.append(show_card(sh, statuses.get(sh.id, SHOW_NEW), lang=lang))
         if len(out) >= 20:
             break
     return out