refactor(calls): drop the deafen iframe-DOM fallback now that the fork owns it (#209)

CallControl.setSound()/applyScreenshareAudioMuted() no longer poke <audio>.muted
inside the EC frame, and the per-membership re-apply (useCallMemberSoundSync)
is gone: with the pin at 0.25.0-lotus.4 the fork applies deafen and the
screenshare-audio mute through its own renderer, including for late joiners.
Verified headless: deafen set before a second participant joins mutes their
track on arrival; deafen/undeafen leaves the screenshare-audio mute in place.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/hooks/useCallEmbed.ts

@@ -13,7 +13,6 @@ import { ThemeKind, useTheme } from './useTheme';
 import { callEmbedAtom } from '../state/callEmbed';
 import { useResizeObserver } from './useResizeObserver';
 import { CallControlState } from '../plugins/call/CallControlState';
-import { useCallMembersChange, useCallSession } from './useCall';
 import { CallPreferences } from '../state/callPreferences';
 import { useSetting } from '../state/hooks/settings';
 import { NoiseSuppressionMode, settingsAtom } from '../state/settings';
@@ -184,14 +183,6 @@ export const useCallHangupEvent = (embed: CallEmbed, callback: () => void) => {
   useClientWidgetApiEvent(embed.call, ElementWidgetActions.Close, callback);
 };
 
-export const useCallMemberSoundSync = (embed: CallEmbed) => {
-  const callSession = useCallSession(embed.room);
-  useCallMembersChange(
-    callSession,
-    useCallback(() => embed.control.applySound(), [embed]),
-  );
-};
-
 export const useCallThemeSync = (embed: CallEmbed) => {
   const theme = useTheme();