perf(plex): batch bulk pushes, cache show enrichment; remove dead code + DRY (F6/F8/F10)

F6: coalesce whole-show/season Plex watch-pushes into ONE background task
(push_bulk_state_to_plex) that reuses a single DB session + keep-alive Plex
client, instead of scheduling one task (own session + HTTP client) per episode.

F8: cache a show's live Plex enrichment (metadata + related) per rating_key for
a short TTL and fetch the two calls in parallel; repeat opens skip the network.
Raw payloads are cached; per-user shaping stays out. An empty related list is not
cached (plex.related swallows a transient failure as [] — don't pin it for the TTL).

F10: remove dead code — the pre-unified /browse route + browse(), the /people
route + people() + _person_photo(), api.plexPeople, interface PlexPerson, and the
orphaned plex.people i18n block. DRY: appendPlexFilters() shared by plexLibrary +
plexFacets; one exported plexDetailUi.Filterable (was Fil + Filterable); PlexInfo
migrated onto the shared plexDetailUi hooks/menu (DetailCustomizeMenu gained
overlay + extra props; useDetailPrefs exposes savePref; PrefToggle exported).

Reviewed (high) → clean. F7 (facet aggregate collapse) deferred: self-exclusion
gives each sub-aggregate a distinct WHERE, and no measurement shows /facets slow.

frontend/src/lib/plexDetailUi.tsx

@@ -1,4 +1,4 @@
-import { useLayoutEffect, useRef, useState } from "react";
+import { useLayoutEffect, useRef, useState, type ReactNode } from "react";
 import { useTranslation } from "react-i18next";
 import { useQueryClient } from "@tanstack/react-query";
 import { SlidersHorizontal } from "lucide-react";
@@ -30,6 +30,7 @@ export function useDetailPrefs() {
     artBg,
     showCast,
     showRelated,
+    savePref: save, // expose the raw persister for callers with extra per-user prefs (e.g. strip sources)
     toggleArtBg: () => {
       const next = !artBg;
       setArtBg(next);
@@ -48,6 +49,28 @@ export function useDetailPrefs() {
   };
 }
 
+// A metadata value that filters the grid when clicked (if onClick is wired), else plain text. Shared
+// by the movie info page (PlexInfo) and the unified grid / show pages (PlexBrowse). The optional
+// `title` gives a hover hint (e.g. "Filter by 1998"); callers that don't need it just omit it.
+export function Filterable({
+  onClick,
+  title,
+  className,
+  children,
+}: {
+  onClick?: () => void;
+  title?: string;
+  className?: string;
+  children: ReactNode;
+}) {
+  if (!onClick) return <span className={className}>{children}</span>;
+  return (
+    <button onClick={onClick} title={title} className={`${className ?? ""} cursor-pointer hover:text-accent transition`}>
+      {children}
+    </button>
+  );
+}
+
 // Paint the item's art as a faint FIXED backdrop on the page's <main> scroll container (HTPC-style),
 // so the glass panels float over it. Cleared on unmount / when disabled / when there's no art.
 export function useArtBackdrop(art: string | null | undefined, enabled: boolean) {
@@ -86,6 +109,8 @@ export function DetailCustomizeMenu({
   showRelated,
   onToggleRelated,
   hasRelated,
+  overlay,
+  extra,
 }: {
   artBg: boolean;
   onToggleArtBg: () => void;
@@ -95,6 +120,8 @@ export function DetailCustomizeMenu({
   showRelated?: boolean;
   onToggleRelated?: () => void;
   hasRelated?: boolean;
+  overlay?: boolean; // white-on-dark button styling when floated over the player
+  extra?: ReactNode; // additional toggles rendered after the built-in ones (e.g. strip-source buckets)
 }) {
   const { t } = useTranslation();
   const [open, setOpen] = useState(false);
@@ -107,7 +134,7 @@ export function DetailCustomizeMenu({
         ref={btnRef}
         onClick={() => setOpen((v) => !v)}
         title={t("plex.info.customize")}
-        className="p-1.5 rounded-lg text-muted hover:bg-surface hover:text-fg"
+        className={`p-1.5 rounded-lg ${overlay ? "text-white/80 hover:bg-white/15" : "text-muted hover:bg-surface hover:text-fg"}`}
       >
         <SlidersHorizontal className="w-4 h-4" />
       </button>
@@ -122,13 +149,14 @@ export function DetailCustomizeMenu({
           {hasRelated && onToggleRelated && (
             <PrefToggle label={t("plex.info.prefRelated")} on={showRelated ?? true} onClick={onToggleRelated} />
           )}
+          {extra}
         </div>
       )}
     </div>
   );
 }
 
-function PrefToggle({ label, on, onClick }: { label: string; on: boolean; onClick: () => void }) {
+export function PrefToggle({ label, on, onClick }: { label: string; on: boolean; onClick: () => void }) {
   return (
     <button
       onClick={onClick}