fix(plex): address S6 code-review — 5 findings

1. (correctness) Show hero rating regression: PlexBrowse's show hero rendered a
   rating only when show.imdb_rating was set, so after the S6 IMDb-only change a
   show with no imdb:// entry showed no rating. Now falls back to the audience
   `rating` like PlexInfo.
2. (correctness) ratingMin column mismatch: the rating filter and the /facets
   rating_max now key off coalesce(imdb_rating, rating) — the SAME "best score"
   the badge displays — so a ratingMin picked from a shown IMDb score narrows the
   right column instead of the raw audience `rating`.
3. (altitude) HU search gap: new query.vector_match() matches EITHER vector in HU
   (or_(search_vector_hu, search_vector)) so a row with no HU twin stays findable
   by its English title; ranking still uses the HU vector. field_recheck unions
   the HU+EN per-field tsvectors in HU, staying a strict subset of the prefilter.
4. (test-coverage) Extracted the badge logic to lib/plexRating.pickRatingBadge
   (shared by PlexInfo + the show hero) with a unit test (imdb-preferred, audience
   fallback, 0-score, none). Backend tests added for the HU union search + the
   IMDb-preferred rating filter.
5. (efficiency) Language switch no longer double-fetches the grid: browseQ is
   gated on a committedLang state that lags `lang` by one render, so the
   genre-clear effect settles into a single fetch instead of one throwaway fetch
   with stale-language genres plus a second.

DB-lane suite 295 passed / 2 skip; FE tsc/knip/lint clean, 217 vitest pass.

backend/app/routes/plex/browse.py

@@ -57,6 +57,7 @@ from app.plex.query import (
     split_csv,
     title_col,
     vector_col,
+    vector_match,
 )
 from app.routes._common import owned_or_404
 from app.routes.plex._shared import item_or_404
@@ -206,7 +207,7 @@ def unified_library(
         if f.duration_max is not None:
             mq = mq.where(PlexItem.duration_s <= f.duration_max)
         if tsq is not None:
-            mq = mq.where(vector_col(PlexItem, lang).op("@@")(tsq))
+            mq = mq.where(vector_match(PlexItem, lang, tsq))
         if recheck is not None:
             mq = mq.where(recheck(PlexItem, field, tsq, lang))
         selects.append(mq)
@@ -251,7 +252,7 @@ def unified_library(
             sq = sq.where(wat == 0, inp == 0)
         sq = apply_meta_filters(sq, PlexShow, p, lang)
         if tsq is not None:
-            sq = sq.where(vector_col(PlexShow, lang).op("@@")(tsq))
+            sq = sq.where(vector_match(PlexShow, lang, tsq))
         if recheck is not None:
             sq = sq.where(recheck(PlexShow, field, tsq, lang))
         selects.append(sq)
@@ -492,10 +493,11 @@ def facets(
             years.append(by[0])
         if by[1] is not None:
             years.append(by[1])
-        # Rating max — exclude the rating filter.
+        # Rating max — exclude the rating filter. Coalesce(imdb, audience) to match the score the
+        # rating filter and the UI badge use (IMDb preferred, audience fallback).
         br = db.scalar(
             wsq(
-                select(func.max(model.rating)),
+                select(func.max(func.coalesce(model.imdb_rating, model.rating))),
                 model,
                 ids,
                 {**p, "rating_min": None},