fix: dispose PeerConnection on call end to release ICE ports

close() alone does not free native WebRTC resources (ICE agent,
ports, threads). Without dispose() the old PC holds ports for ~30s,
blocking the next call from connecting.

app/src/main/java/com/rosetta/messenger/network/CallManager.kt

@@ -871,7 +871,11 @@ object CallManager {
         runCatching { localAudioTrack?.setEnabled(false) }
         runCatching { localAudioTrack?.dispose() }
         runCatching { audioSource?.dispose() }
+        // close() stops media but does NOT release native resources (ICE agent,
+        // ports, OWTF threads). Without dispose() the old PC keeps ports bound
+        // for ~30 s, blocking the next call from connecting.
         runCatching { peerConnection?.close() }
+        runCatching { peerConnection?.dispose() }
         localAudioTrack = null
         audioSource = null
         peerConnection = null