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/state/settings.ts

@@ -286,6 +286,8 @@ export interface Settings {
   fontFamily: 'system' | 'inter' | 'jetbrains-mono' | 'fira-code';
 
   afkAutoMute: boolean;
+  /** [Gitea #117] 'You're muted' nudge when talking into a muted mic. */
+  mutedTalkWarning: boolean;
   afkTimeoutMinutes: number;
 
   callJoinLeaveSound: 'off' | 'chime' | 'soft' | 'retro';
@@ -402,6 +404,7 @@ const defaultSettings: Settings = {
   fontFamily: 'inter',
 
   afkAutoMute: false,
+  mutedTalkWarning: true,
   afkTimeoutMinutes: 10,
 
   callJoinLeaveSound: 'chime',