Adjust commit frequency from every 100 messages back to every 50 messages
to provide better balance between throughput and fault tolerance.
Every 100 messages was too aggressive - test showed 98% message loss.
Every 50 messages (1,000/50 = ~24 commits per 1000 msgs) provides:
- Reasonable throughput improvement vs every 10 (188 commits)
- Bounded message loss window if consumer fails (~50 messages)
- Auto-commit (100ms interval) provides additional failsafe