E5 S3: unified Plex card — scrim-reveal hover + rest polish

The poster card (grid + person page) gets the Seerr-style hover: on hover a
bottom scrim slides up with the title, a "year · runtime · ★rating" meta line,
and a 3-line synopsis — the info you'd otherwise click through for — plus a
less-flat play ring (radial-gradient + ring shadow) and a top-right quick-action
cluster (Info + watched-toggle, revealed on hover / always on touch). Rest-state
badges (season / type tag) yield to the scrim on hover; the playable-cost tint
stays. (§1 A + C from the enrichment study.)

Backend (the data the scrim needs, mirroring S1's `art`): the grid
(browse.unified_library) now emits a lang-coalesced, truncated `summary` (new
query.summary_col) + the Plex `rating`; movie_card/show_card do the same (EN) for
the detail/related/person cards. PlexCard.rating type added (summary already
existed for episodes).

Gate: tsc x3 / eslint / prettier / knip / vitest 326 green; ruff green; backend
lane full suite green. Self-E2E on the live dev server (rebuilt on this branch,
S2-enriched): the grid serves rating+summary (Shawshank 9.3, Godfather 9.2, real
synopses) and the card renders the play ring + scrim (The Expanse: ring, synopsis,
★8.1) — verified via the DOM (the pane wouldn't composite for a screenshot).

backend/app/plex/query.py

@@ -29,6 +29,11 @@ def title_col(model, lang: str):
     return func.coalesce(model.title_hu, model.title) if lang == "hu" else model.title
 
 
+def summary_col(model, lang: str):
+    """DISPLAY summary, HU-coalesced (EN fallback) — the card hover-overview + info page read this."""
+    return func.coalesce(model.summary_hu, model.summary) if lang == "hu" else model.summary
+
+
 def genres_col(model, lang: str):
     # type_coerce so the JSONB comparator (`.contains` / `@>`, GIN-backed) survives the coalesce.
     if lang == "hu":