feat(calls): 'You're muted' nudge when talking into a muted mic (#117)

Host half of the talking-while-muted feature. The fork (0.25.0-lotus.9)
reports speakingWhileMuted for the local participant in io.lotus.call_state —
a level tap on the muted track, so cinny captures no audio. useMutedTalkWarning
polls that flag while muted; after 1.5 s of it being true it shows one sticky
toast, "You're muted — click to unmute", whose click unmutes; it fires at most
once per mute session (re-arms after unmute → mute), is retired the moment the
mic comes back on by any means, and never runs in Push-to-Talk mode. Setting
'Warn me when I talk while muted' (default on) sits next to AFK Auto-Mute.

Verified headless with a tone mic: no toast at +1 s, toast at +4 s, click
unmutes and clears it, second mute re-arms, unmute via the button clears it,
PTT mode → nothing.

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

src/app/components/CallEmbedProvider.tsx

@@ -48,6 +48,7 @@ import { useCallMembersChange, useCallSession } from '../hooks/useCall';
 import { useCallJoinLeaveSounds } from '../hooks/useCallJoinLeaveSounds';
 import { useCallPolicyRevokedToast } from '../hooks/useCallPolicyRevokedToast';
 import { useCallAnnouncements } from '../hooks/useCallAnnouncements';
+import { useMutedTalkWarning } from '../hooks/useMutedTalkWarning';
 import { callAnnouncementAtom } from '../state/callAnnouncement';
 import { SrOnly } from '../features/call-status/styles.css';
 import { useCallHotkeys } from '../hooks/useCallHotkeys';
@@ -744,6 +745,7 @@ function CallUtils({ embed, joined }: { embed: CallEmbed; joined: boolean }) {
   useCallJoinLeaveSounds(embed);
   useCallPolicyRevokedToast(embed, joined);
   useCallAnnouncements(embed, joined);
+  useMutedTalkWarning(embed, joined);
   useCallThemeSync(embed);
   useCallQuality(embed);
   useCallHangupEvent(