feat(filters): scope global feed filters in FeedFiltersProvider

Lift the feed's filter god-state (per-account persistence, the account-load
effect, share-link capture) out of App into a split-context provider mirroring
NavigationProvider. Sidebar/Header/NotificationsPanel read it via hooks instead
of prop-drilling; <Feed> keeps its filters prop since ChannelPage renders it with
its own channel-scoped state.

frontend/src/components/Header.tsx

@@ -1,20 +1,19 @@
 import { type ReactNode } from "react";
 import { useTranslation } from "react-i18next";
 import { Youtube } from "lucide-react";
-import type { FeedFilters, Me } from "../lib/api";
+import type { Me } from "../lib/api";
 import { moduleLabelKey, moduleOrder, stepModule } from "../lib/modules";
 import ModuleName from "./ModuleName";
 import SearchBar from "./SearchBar";
 import SyncStatus from "./SyncStatus";
 import { useNavigation, useNavigationActions } from "./NavigationProvider";
+import { useFeedFilters, useFeedFiltersActions } from "./FeedFiltersProvider";
 
 // The floating top header: a row of glass pills over the content — a ModuleName pill (label +
 // accent dot + back/forward arrows), the module's SearchBar where it has one, and the per-user
 // sync chip at the right end.
 export default function Header({
   me,
-  filters,
-  setFilters,
   plexQ,
   setPlexQ,
   channelsSearch,
@@ -25,8 +24,6 @@ export default function Header({
   onGoToFullHistory,
 }: {
   me: Me;
-  filters: FeedFilters;
-  setFilters: (f: FeedFilters) => void;
   // Plex has its own ephemeral search term (see App) — the box is shared UI, the state is not.
   plexQ: string;
   setPlexQ: (q: string) => void;
@@ -43,6 +40,8 @@ export default function Header({
   const { t } = useTranslation();
   const { page } = useNavigation();
   const { setPage } = useNavigationActions();
+  const filters = useFeedFilters();
+  const { setFilters } = useFeedFiltersActions();
   // The ◀/▶ arrows step cyclically through the user's available modules (derived from `me`, so
   // it stays correct as modules are added/gated). Labels of every active module feed ModuleName's
   // dynamic width so the pill is sized to the widest reachable title in the current language.