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/routes/plex/browse.py

@@ -38,6 +38,7 @@ from app.plex.query import (
     movie_status_case,
     show_status_case,
     split_csv,
+    summary_col,
     title_col,
     vector_col,
     vector_match,
@@ -130,6 +131,8 @@ def unified_library(
                 title_col(PlexItem, lang).label("title"),
                 PlexItem.year.label("year"),
                 PlexItem.rating.label("rating"),
+                # Truncated so the card hover-overview costs a few hundred bytes, not the full synopsis.
+                func.left(summary_col(PlexItem, lang), 300).label("summary"),
                 PlexItem.added_at.label("added_at"),
                 PlexItem.originally_available_at.label("rel"),
                 PlexItem.duration_s.label("duration_s"),
@@ -170,6 +173,7 @@ def unified_library(
                 title_col(PlexShow, lang).label("title"),
                 PlexShow.year.label("year"),
                 PlexShow.rating.label("rating"),
+                func.left(summary_col(PlexShow, lang), 300).label("summary"),
                 PlexShow.added_at.label("added_at"),
                 PlexShow.originally_available_at.label("rel"),
                 cast(null(), Integer).label("duration_s"),
@@ -227,6 +231,8 @@ def unified_library(
                         "type": "movie",
                         "title": r.title,
                         "year": r.year,
+                        "rating": r.rating,
+                        "summary": r.summary,
                         "duration_seconds": r.duration_s,
                         "thumb": f"/api/plex/image/{r.rk}",
                         "playable": r.playable,
@@ -241,6 +247,8 @@ def unified_library(
                         "type": "show",
                         "title": r.title,
                         "year": r.year,
+                        "rating": r.rating,
+                        "summary": r.summary,
                         "thumb": f"/api/plex/image/{r.rk}",
                         "season_count": r.season_count,
                         "status": r.status,