feat(plex): a title opens its page, the picture plays; an episode links up

A card title lit like a link but played the item. Now the picture plays and
the title opens the page of what it names: a movie's or an episode's info
page, a show's page, and for an episode standing as its show (Recently
watched) the show. Every poster and episode card carries it (grid, rails,
person, collection, season, related, Home), a card with no page keeps a plain
title, and the season page gains the menu's Details row too.

The episode page had no way up: the detail now serves the show's and the
season's rating keys, and on the page the show title opens the show and
"S1·E25" the season (Back returns to where the page was).

backend/tests/test_plex_detail.py

@@ -19,7 +19,7 @@ import app.state as state
 from app.auth import current_user
 from app.db import get_db
 from app.main import app
-from app.models import PlexItem, PlexLibrary, PlexShow, User
+from app.models import PlexItem, PlexLibrary, PlexSeason, PlexShow, User
 from app.plex import detail
 from app.plex.sync import _apply_facet_fields, _enrich_people_batch
 
@@ -276,8 +276,16 @@ def test_item_detail_episode_serves_rich_from_live(db, monkeypatch, override_dep
     show = PlexShow(rating_key="s1", library_id=lib.id, title="A Show")
     db.add(show)
     db.flush()
+    season = PlexSeason(rating_key="se1", show_id=show.id, season_number=1)
+    db.add(season)
+    db.flush()
     ep = PlexItem(
-        rating_key="e1", library_id=lib.id, kind="episode", title="Pilot", show_id=show.id
+        rating_key="e1",
+        library_id=lib.id,
+        kind="episode",
+        title="Pilot",
+        show_id=show.id,
+        season_id=season.id,
     )
     db.add(ep)
     db.commit()
@@ -289,6 +297,8 @@ def test_item_detail_episode_serves_rich_from_live(db, monkeypatch, override_dep
     assert resp.status_code == 200, resp.text
     body = resp.json()
     assert body["imdb_id"] == "tt0068646"  # from the live meta, not the (NULL) row
+    # The page's links up to the show and the season.
+    assert (body["show_id"], body["season_id"]) == ("s1", "se1")
     assert [c["name"] for c in body["cast"]] == ["Marlon Brando", "Al Pacino"]
     db.refresh(ep)
     assert ep.full_cast is None  # episodes are not persisted/enriched