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/discover/pins.py

@@ -24,7 +24,7 @@ from sqlalchemy.orm import Session
 from app.discover import cards, queries
 from app.models import Channel, ComfortPin, PlexItem, PlexShow, Playlist, User, Video
 from app.plex import rollup
-from app.plex.cards import leaf_card, show_card
+from app.plex.cards import SHOW_NEW, leaf_card, show_card
 from app.plex.lookups import by_rating_key
 
 # kind -> the ComfortPin column that holds it. The client's vocabulary and the schema's, in one place.
@@ -203,8 +203,8 @@ def _shelf_card(db: Session, user: User, pin: ComfortPin, batch: _Batch, lang: s
         sh = db.get(PlexShow, pin.plex_show_id)
         if sh is None:
             return None
-        status = rollup.state_map(db, user.id, [sh.id]).get(sh.id, "new")
-        card = cards.from_plex(show_card(sh, status, lang=lang))
+        state = rollup.state_map(db, user.id, [sh.id]).get(sh.id, SHOW_NEW)
+        card = cards.from_plex(show_card(sh, state, lang=lang))
         ep = queries.next_episode(db, user.id, sh.id, lang=lang)
         nxt = cards.from_plex(ep) if ep else None