Make it possible to retry the video recording if it fails

[zachm-vapi]

Linear: VAPICS-1170

When call.startRecording() is called, the client must become ready within 25 seconds, or Daily will time out. If the client fails to become ready (e.g. due to a slow connection), Daily will emit a recording-error event, and the call will not be recorded.

This commit exposes public startRecording() and stopRecording() methods so that the developer can choose to retry the recording if it fails for whatever reason.

For example:

vapi.on('recording-error', (e) => {
  console.error('Recording failed', e);
  // Retry after a short delay
  setTimeout(() => vapi.startRecording(), 5000);
});