feat: knock notifications for admins + AFK auto-mute in calls

P4-3 — Knock-to-join Notifications for Admins:
- usePendingKnocks() hook reactively tracks knocking members via
  RoomMemberEvent.Membership; returns empty array if user lacks invite power
- Members icon in RoomViewHeader shows a Warning badge with the knock count
  when there are pending requests; badge updates in real time without
  needing to open the drawer; aria-label updated to describe pending count

P5-11 — AFK Auto-Mute in Voice:
- useAfkAutoMute() hook opens a monitoring-only getUserMedia stream,
  connects it to an AnalyserNode, and polls RMS every 500ms
- If mic is on and RMS stays below threshold for the configured timeout,
  calls callEmbed.control.setMicrophone(false) and shows an in-app toast
- Hook is called inside CallControls so monitoring is only active during calls
- Settings: afkAutoMute toggle + afkTimeoutMinutes select (1/5/10/20/30 min,
  default 10) added to Settings → Calls

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/call/CallControls.tsx

@@ -35,6 +35,7 @@ import { useResizeObserver } from '../../hooks/useResizeObserver';
 import { stopPropagation } from '../../utils/keyboard';
 import { AsyncStatus, useAsyncCallback } from '../../hooks/useAsyncCallback';
 import { useCallEmbedRef } from '../../hooks/useCallEmbed';
+import { useAfkAutoMute } from '../../hooks/useAfkAutoMute';
 
 type CallControlsProps = {
   callEmbed: CallEmbed;
@@ -71,6 +72,8 @@ export function CallControls({ callEmbed }: CallControlsProps) {
   const { microphone, video, sound, screenshare, spotlight, screenshareAudioMuted } =
     useCallControlState(callEmbed.control);
 
+  useAfkAutoMute(callEmbed);
+
   const [cords, setCords] = useState<RectCords>();
   const [shareConfirm, setShareConfirm] = useState(false);
   useEffect(() => {