refactor: improve separation of concerns in call feature

1. Move UI toggle state out of CallState.Connected:
   - Removed isAudioMuted/isVideoEnabled/isSpeakerOn from domain
     CallState. These are UI concerns, not call state.
   - Added StateFlows for toggles in CallController (isAudioMuted,
     isVideoEnabled, isSpeakerOn) with proper toggle methods.
   - CallScreen reads toggle state from CallController flows.
   - Removed toggleAudioMute/toggleVideo/toggleSpeaker from
     CallManager (no longer manages UI state).

2. Move ICE candidate parsing to quartz layer:
   - Added candidateSdp(), sdpMid(), sdpMLineIndex() parsers and
     serializeCandidate() to CallIceCandidateEvent in quartz.
   - Removed companion object with parseIceCandidate/
     serializeIceCandidate from CallController.
   - CallController now uses quartz-layer parsing directly.
   - Updated IceCandidateSerializationTest accordingly.

3. Add helper methods to CallManager:
   - currentCallId() and currentPeerPubKey() extract from any
     active state, reducing repeated when expressions.

4. Fix empty callId bug in ChatroomScreen:
   - Navigation to ActiveCall now uses callManager.currentCallId()
     instead of hardcoded empty string.

https://claude.ai/code/session_017hZm7yu7CzmcQgZGSaqSXS

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/call/CallManager.kt

@@ -216,26 +216,23 @@ class CallManager(
         }
     }
 
-    fun toggleAudioMute() {
-        val current = _state.value
-        if (current is CallState.Connected) {
-            _state.value = current.copy(isAudioMuted = !current.isAudioMuted)
+    fun currentCallId(): String? =
+        when (val s = _state.value) {
+            is CallState.Offering -> s.callId
+            is CallState.IncomingCall -> s.callId
+            is CallState.Connecting -> s.callId
+            is CallState.Connected -> s.callId
+            else -> null
         }
-    }
 
-    fun toggleVideo() {
-        val current = _state.value
-        if (current is CallState.Connected) {
-            _state.value = current.copy(isVideoEnabled = !current.isVideoEnabled)
+    fun currentPeerPubKey(): HexKey? =
+        when (val s = _state.value) {
+            is CallState.Offering -> s.peerPubKey
+            is CallState.IncomingCall -> s.callerPubKey
+            is CallState.Connecting -> s.peerPubKey
+            is CallState.Connected -> s.peerPubKey
+            else -> null
         }
-    }
-
-    fun toggleSpeaker() {
-        val current = _state.value
-        if (current is CallState.Connected) {
-            _state.value = current.copy(isSpeakerOn = !current.isSpeakerOn)
-        }
-    }
 
     fun reset() {
         _state.value = CallState.Idle

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/call/CallState.kt

@@ -52,9 +52,6 @@ sealed interface CallState {
         val peerPubKey: HexKey,
         val callType: CallType,
         val startedAtEpoch: Long,
-        val isAudioMuted: Boolean = false,
-        val isVideoEnabled: Boolean = true,
-        val isSpeakerOn: Boolean = false,
     ) : CallState
 
     data class Ended(