feat: animate local speaker ring from MoQ frame transmission

Wire the local user's avatar into the existing speaking-ring animation so
the host/speaker sees the same green ring + amplitude glow on their own
cell that remote speakers already get.

Ground truth is the broadcaster's `publisher.send(opus)` success: the new
`onLevel` callback fires only after a frame actually leaves on the wire,
computed from the raw PCM peak (shared `peakAmplitude` util used by both
the player decode loop and the broadcaster capture loop). This means the
animation reflects what the relay sees, not any UI-side mute / role
state that could be stale or buggy — if frames are flowing, the ring
plays.

Plumbing: `NestsSpeaker.startBroadcasting` gains an optional `onLevel`
that the moq-lite + IETF broadcasters both honour, the reconnecting
wrapper replays it on every session reissue (alongside the existing
mute-intent replay), and `NestViewModel.startBroadcast` hands it a
lambda that calls the existing `onSpeakerActivity` / `onAudioLevel`
plumbing keyed on the local pubkey. The 250 ms speaking-timeout fades
the ring naturally when the user mutes or stops broadcasting.

nestsClient/src/commonMain/kotlin/com/vitorpamplona/nestsclient/NestsConnect.kt

@@ -260,7 +260,7 @@ private fun failedSpeaker(state: MutableStateFlow<NestsSpeakerState>): NestsSpea
     object : NestsSpeaker {
         override val state = state
 
-        override suspend fun startBroadcasting(): BroadcastHandle = error("speaker never connected: ${state.value}")
+        override suspend fun startBroadcasting(onLevel: (Float) -> Unit): BroadcastHandle = error("speaker never connected: ${state.value}")
 
         override suspend fun close() {
             if (state.value !is NestsSpeakerState.Closed) {