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/app/routes/plex/detail.py

@@ -504,6 +504,7 @@ def item_detail(
 
     prev_id, next_id = _episode_nav(db, it)
     show = db.get(PlexShow, it.show_id) if it.kind == "episode" and it.show_id else None
+    season = db.get(PlexSeason, it.season_id) if show and it.season_id else None
     return {
         "id": it.rating_key,
         "kind": it.kind,
@@ -537,6 +538,9 @@ def item_detail(
         "status": st.status if st else "new",
         "position_seconds": st.position_seconds if st else 0,
         "show_title": ((show.title_hu or show.title if hu else show.title) if show else None),
+        # The episode page links up to its show and its season (their rating keys = the view keys).
+        "show_id": show.rating_key if show else None,
+        "season_id": season.rating_key if season else None,
         "season_number": it.season_number,
         "episode_number": it.episode_number,
         "prev_id": prev_id,