Ends the call and releases all WebRTC resources.
Sends a Verto bye to the server, transitions status$ to disconnecting then disconnected, and destroys the call instance. After the promise resolves, the call object is no longer usable — drop your reference and let it be garbage-collected.
The promise resolves once the local teardown has completed. Server-side cleanup (recording finalization, billing) continues asynchronously and is not awaited.
Promise<void> — resolves when the local teardown has completed.