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/sync.py

@@ -24,6 +24,7 @@ from app import logs, sysconfig
 from app.models import PlexCollection, PlexItem, PlexLibrary, PlexSeason, PlexShow
 from app.plex import detail, people
 from app.plex.client import PlexClient, PlexError, PlexNotConfigured
+from app.plex.genres import hu_genres
 from app.plex.lookups import by_rating_key
 
 log = logs.get_logger(__name__)
@@ -659,35 +660,66 @@ def _sync_overlay(
     db: Session, plex: PlexClient, lib: PlexLibrary, en_lib_id: int, stats: dict
 ) -> None:
     """Write an overlay section's Hungarian metadata onto its EN twin's rows, matched by guid. Creates
-    NO browsable rows — an overlay library is never listed on its own. Only title/summary/genres differ
-    by language; the language-neutral people_text feeds both search vectors.
+    NO browsable rows — an overlay library is never listed on its own. Only title/summary/tagline/genres
+    differ by language; the language-neutral people_text feeds both search vectors. A show section's
+    episodes are overlaid too (E30): the HU section lists every episode with its Hungarian title and
+    summary, and the episode rows live in the EN show library.
 
     This is a full RECONCILE: every guid-bearing EN row's HU fields are cleared first, then the HU
     section repopulates the matches — so an EN row whose HU twin vanished (or was re-guid'd) falls back
     to EN instead of keeping stale Hungarian metadata. HU items with no EN match are skipped."""
     if lib.kind == "movie":
-        rows = db.execute(
-            select(PlexItem).where(
-                PlexItem.library_id == en_lib_id,
-                PlexItem.kind == "movie",
-                PlexItem.guid.is_not(None),
+        passes = [
+            (
+                _TYPE_MOVIE,
+                select(PlexItem).where(
+                    PlexItem.library_id == en_lib_id,
+                    PlexItem.kind == "movie",
+                    PlexItem.guid.is_not(None),
+                ),
             )
-        ).scalars()
-        item_type = _TYPE_MOVIE
+        ]
     else:
-        rows = db.execute(
-            select(PlexShow).where(PlexShow.library_id == en_lib_id, PlexShow.guid.is_not(None))
-        ).scalars()
-        item_type = _TYPE_SHOW
+        passes = [
+            (
+                _TYPE_SHOW,
+                select(PlexShow).where(
+                    PlexShow.library_id == en_lib_id, PlexShow.guid.is_not(None)
+                ),
+            ),
+            (
+                _TYPE_EPISODE,
+                select(PlexItem).where(
+                    PlexItem.library_id == en_lib_id,
+                    PlexItem.kind == "episode",
+                    PlexItem.guid.is_not(None),
+                ),
+            ),
+        ]
+    for item_type, rows_q in passes:
+        _overlay_pass(db, plex, lib, item_type, db.execute(rows_q).scalars(), stats)
+    db.flush()
+
+
+def _overlay_pass(
+    db: Session, plex: PlexClient, lib: PlexLibrary, item_type: int, rows, stats: dict
+):
+    """One kind of the overlay (movies, shows or episodes) — see `_sync_overlay`."""
     # guid -> the EN rows carrying it (a list: two editions of one film can share a guid; both overlay).
     by_guid: dict[str, list] = {}
     for r in rows:
         by_guid.setdefault(r.guid, []).append(r)
     # Reconcile step: clear HU fields on all guid-bearing rows. Only rows that actually held HU data
     # become dirty (SQLAlchemy skips a no-net-change UPDATE), so this is cheap; matches are re-set below.
+    # The genres are the exception: every row gets Hungarian ones, from its HU twin or, lacking one, from
+    # its own English list — otherwise the HU genre list mixed "Drama" (no twin) with "Dráma".
+    episodes = item_type == _TYPE_EPISODE
     for group in by_guid.values():
         for row in group:
-            row.title_hu = row.summary_hu = row.genres_hu = None
+            row.title_hu = row.summary_hu = None
+            if not episodes:
+                row.tagline_hu = None
+                row.genres_hu = hu_genres(row.genres)
     seen: set[str] = (
         set()
     )  # first HU entry for a guid wins; a dup HU item can't overwrite or double-count
@@ -699,13 +731,15 @@ def _sync_overlay(
         seen.add(g)
         title_hu = (meta.get("title") or "").strip() or None
         summary_hu = meta.get("summary")
-        genres_hu = _tags(meta, "Genre")
+        tagline_hu = (meta.get("tagline") or "").strip() or None
+        genres_hu = hu_genres(_tags(meta, "Genre"))
         for row in targets:
             row.title_hu = title_hu
             row.summary_hu = summary_hu
-            row.genres_hu = genres_hu
+            if not episodes:
+                row.tagline_hu = tagline_hu
+                row.genres_hu = genres_hu or row.genres_hu
         stats["overlaid"] = stats.get("overlaid", 0) + 1
-    db.flush()
 
 
 def _upsert_collection(