refactor(plex): scope module state in PlexProvider

Lift the Plex module's shared local state (scope / watch-state / sort / expanded
filters / search term / open-playlist hand-off) out of App into a split-context
PlexProvider with stable useCallback setters. PlexSidebar, PlexBrowse, and the
header search box read it via usePlex()/usePlexActions() instead of props drilled
through App; PlexBrowse is now prop-free. App loses six useStates + the filters
JSON memo/serialise helpers. (Platform S6b.2)

frontend/src/App.tsx

@@ -3,11 +3,9 @@ import { useTranslation } from "react-i18next";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import {
   api,
-  EMPTY_PLEX_FILTERS,
   getActiveAccount,
   setActiveAccount,
   setUnauthorizedHandler,
-  type PlexFilters,
 } from "./lib/api";
 import { setLanguage, isSupported, type LangCode } from "./i18n";
 import {
@@ -156,30 +154,6 @@ export default function App() {
       : channelsViewRaw === "blocked"
         ? "blocked"
         : "subscribed";
-  // Plex module filters (its own left-sidebar filter section) — per-account persisted.
-  // The former per-library picker is now a cross-library SCOPE: movie | show | both (unified library).
-  // (Reuses the old LS.plexLibrary key; an old stored library-id value falls back to "both".)
-  const [plexScopeRaw, setPlexScope] = useAccountPersistedState(LS.plexLibrary, "both");
-  const plexScope = ["movie", "show", "both"].includes(plexScopeRaw) ? plexScopeRaw : "both";
-  const [plexShowFilter, setPlexShowFilter] = useAccountPersistedState(LS.plexShow, "all");
-  const [plexSort, setPlexSort] = useAccountPersistedState(LS.plexSort, "title");
-  const [plexPlaylistOpen, setPlexPlaylistOpen] = useState<number | null>(null); // sidebar → open a playlist
-  // The expanded Plex filters live as one JSON blob (the string-only account store serializes it).
-  const [plexFiltersRaw, setPlexFiltersRaw] = useAccountPersistedState(LS.plexFilters, "{}");
-  const plexFilters = useMemo<PlexFilters>(() => {
-    try {
-      return { ...EMPTY_PLEX_FILTERS, ...JSON.parse(plexFiltersRaw) };
-    } catch {
-      return EMPTY_PLEX_FILTERS;
-    }
-  }, [plexFiltersRaw]);
-  const setPlexFilters = (f: PlexFilters) => setPlexFiltersRaw(JSON.stringify(f));
-  // The Plex library search term is its OWN ephemeral state — deliberately NOT the persisted feed
-  // `filters.q`. Sharing that box meant a Plex search leaked into the feed and, being persisted,
-  // greeted you with a stale query (colliding with a persisted collection filter → confusing
-  // "0 matches") after a reload. Kept in App so it survives page switches within a session, but
-  // resets on reload.
-  const [plexQ, setPlexQ] = useAccountPersistedState(LS.plexQ, ""); // survives F5, unlike the feed search
   // Bumped to tell the channel manager to drop a stale column filter when we send the user
   // there to see a specific set (the header's "without full history" link).
   const [channelsFilterReset, setChannelsFilterReset] = useState(0);
@@ -581,15 +555,6 @@ export default function App() {
       {page === "plex" && meQuery.data!.plex_enabled && (
         <Suspense fallback={null}>
           <PlexSidebar
-            scope={plexScope}
-            setScope={setPlexScope}
-            show={plexShowFilter}
-            setShow={setPlexShowFilter}
-            sort={plexSort}
-            setSort={setPlexSort}
-            filters={plexFilters}
-            setFilters={setPlexFilters}
-            onOpenPlaylist={setPlexPlaylistOpen}
             layout={panelLayouts.plex}
             setLayout={(l) => setPanelLayout("plex", l)}
             collapsed={filterCollapsed}
@@ -644,8 +609,6 @@ export default function App() {
             header={
               <Header
                 me={meQuery.data!}
-                plexQ={plexQ}
-                setPlexQ={setPlexQ}
                 channelsSearch={channelsSearch}
                 setChannelsSearch={setChannelsSearch}
                 onYtSearch={enterYtSearch}
@@ -714,17 +677,7 @@ export default function App() {
               onOpenWizard={() => setWizardOpen(true)}
             />
           ) : page === "plex" && meQuery.data!.plex_enabled ? (
-            <PlexBrowse
-              q={plexQ}
-              scope={plexScope}
-              setScope={setPlexScope}
-              show={plexShowFilter}
-              sort={plexSort}
-              filters={plexFilters}
-              setFilters={setPlexFilters}
-              openPlaylist={plexPlaylistOpen}
-              onPlaylistOpened={() => setPlexPlaylistOpen(null)}
-            />
+            <PlexBrowse />
           ) : (
             <Feed
               filters={filters}