feat(plex): TV-show metadata sync + series filters (Phase 1 of series view)

Give TV shows the same filterable metadata as movies so the TV grid can be
filtered/sorted, not just library+sort. Backend: migration 0052 adds
rating/content_rating/studio/originally_available_at/genres/directors/cast_names/
people_text to plex_shows (+ GIN/indexes, people_text folded into search_vector);
_sync_shows populates them cheaply from the show section listing (no per-item
calls). /browse show-branch gains the movie filter set (minus duration) plus an
aggregate per-user watch-state (a show rolls up its episodes: all watched=watched,
any progress=in_progress, none=new) with year/rating/release sorts; /facets returns
show facets. Frontend: PlexSidebar renders the metadata filters + watch-state for TV
libraries (duration stays movie-only); show cards show a watched/in-progress badge.
i18n plex.inProgress (en/hu/de). Needs a Plex re-sync to populate the new columns.

frontend/src/components/PlexBrowse.tsx

@@ -406,6 +406,12 @@ function PlexPosterCard({
             {t("plex.seasons", { count: card.season_count })}
           </span>
         )}
+        {/* Aggregate in-progress badge for a partially-watched show. */}
+        {card.type === "show" && card.status === "in_progress" && (
+          <span className="absolute top-1.5 right-1.5 text-[10px] bg-accent/80 text-accent-fg px-1.5 py-0.5 rounded group-hover:opacity-0">
+            {t("plex.inProgress")}
+          </span>
+        )}
         {card.playable && (
           <span
             className={`absolute top-1.5 left-1.5 w-2 h-2 rounded-full ${PLAYABLE_TINT[card.playable] ?? "bg-gray-400"}`}