fix(deferred): close frontend UI/UX tails from the hygiene sweep

- player YB2: keepalive pagehide beacon (api.saveProgressBeacon) so the resume
  position isn't lost on F5/close within 5s of the last checkpoint (mirrors Plex).
- player YB4: bound consecutive unplayable items in auto-advance so an
  auto-advancing/loop=all queue can't spin over a run of dead videos.
- downloads B6 (client): localise structured quota/edit errors centrally in
  api.req() via localizeDetail() + Intl.NumberFormat (fixes HU/DE + decimal sep);
  + 3-locale download error strings.
- channels FB1: focusChannelToken bump so re-clicking the same channel re-seeds
  the search box; FB2: syncSubs invalidates feed/feed-count (set can change now).
- config CB2: reseed the ConfigPanel draft on a key-set dataVersion + explicit
  post-save token, so a mid-edit refetch can't clobber an in-progress edit.
- config AB3 (UI): a blank allow_empty field stores "" instead of resetting.
- admin SB2/SC2: confirm + success toast on demo-whitelist remove and deny-invite
  (+ trilingual strings); SC1: disable only the acted-on row (pendingId), not all;
  SB3: pause the 1s scheduler countdown ticker while the tab is hidden.
- messages CT4: only invalidate conversations/unread when the incoming-message
  count actually changed, not on every 20s poll; MB3 (client): react to the live
  unread ping (onUnread → invalidate); MC3: extract e2ee installKey (setup/unlock);
  CC2: hoist POLL_MS to messaging.ts; MB4: document the reload-scoped socket.

frontend/src/components/Channels.tsx

@@ -48,6 +48,7 @@ export default function Channels({
   onFilterByTag,
   onFocusChannel,
   focusChannelName,
+  focusChannelToken,
   statusFilter,
   setStatusFilter,
   view,
@@ -61,6 +62,9 @@ export default function Channels({
   onFilterByTag: (tagId: number, name: string) => void;
   onFocusChannel: (name: string) => void;
   focusChannelName: string | null;
+  // Bumped every time a focus-channel intent is (re-)issued, so re-clicking the same channel
+  // re-seeds the search box even when the name is unchanged.
+  focusChannelToken: number;
   statusFilter: ChannelStatusFilter;
   setStatusFilter: (f: ChannelStatusFilter) => void;
   // The active tab lives in App so navigation intents that target the subscriptions table
@@ -92,6 +96,10 @@ export default function Channels({
     qc.invalidateQueries({ queryKey: ["channels"] });
     qc.invalidateQueries({ queryKey: ["tags"] });
     qc.invalidateQueries({ queryKey: ["my-status"] });
+    // FB2: syncing subscriptions can change the feed immediately — newly-followed channels may
+    // already have videos in the shared catalog, so refresh the feed too (not just the manager).
+    qc.invalidateQueries({ queryKey: ["feed"] });
+    qc.invalidateQueries({ queryKey: ["feed-count"] });
   };
 
   const userTags = (tagsQuery.data ?? []).filter((t) => !t.system);
@@ -189,7 +197,8 @@ export default function Channels({
   // A focus-channel intent (header "without full history" / tag manager) seeds the search box.
   useEffect(() => {
     if (focusChannelName) setSearch(focusChannelName);
-  }, [focusChannelName]);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [focusChannelToken]);
   // The header's reset intent clears the search + tag chips (skip the initial mount).
   const resetRef = useRef(filtersResetToken);
   useEffect(() => {