feat(plex): episodes, taglines and genres in Hungarian from the HU overlay (E30 S1a)

The HU TV section lists every episode with its Hungarian title and summary, but the
overlay read only movies and shows, so every episode stayed English. It now overlays
the episodes too, and the HU tagline (new tagline_hu column, served on ?lang=hu).

Plex's HU agent returns a mixed genre vocabulary (Action beside Dráma), and a title
with no HU twin kept its English list, so the HU genre list showed Drama and Dráma.
plex/genres.py maps every genre word to one Hungarian word; the overlay writes it
into genres_hu for every row, and a HU genre filter is read through the same map,
so a saved filter still holding Action keeps matching.

backend/app/plex/query.py

@@ -11,6 +11,7 @@ from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Session
 
 from app.models import PlexItem, PlexLibrary
+from app.plex.genres import hu_genre
 
 TS_CONFIG = "public.unaccent_simple"
 
@@ -181,6 +182,10 @@ def meta_filter_conds(model, p: dict, lang: str = "en") -> list:
     Genre chips are language-specific strings, so they filter the active-language genre column."""
     conds: list = []
     gsel = split_csv(p.get("genres"))
+    if gsel and lang == "hu":
+        # The HU column holds one Hungarian word per genre (plex/genres.py); a filter saved while it
+        # still offered "Action" is read as "Akció", so it keeps matching instead of emptying the grid.
+        gsel = list(dict.fromkeys(hu_genre(g) for g in gsel))
     if gsel:
         gcol = genres_col(model, lang)
         gc = [gcol.contains([g]) for g in gsel]