use franz as new kafka lib

[gokutheengineer]

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[github-actions]

🤖 Claude Code Review

Status: Complete

This PR migrates from IBM Sarama to franz-go as the Kafka client library, significantly simplifying the codebase by reducing abstraction layers.

Issues Found:

1. Potential goroutine leak in util/kafka/in_memory_kafka/in_memory_kafka.go:487-500 - The goroutine in InMemoryConsumerGroupClaim.Messages() that filters messages based on pause state lacks a cleanup mechanism. If the consumer stops reading from the filtered channel, the goroutine will block indefinitely on filtered <- msg, potentially accumulating in long-running test suites. Consider adding context-aware cleanup or a timeout to prevent indefinite blocking.

Architecture Changes:

• Removed Sarama dependency, adopted franz-go (more modern, better performance)
• Simplified in-memory Kafka mock (removed complex Sarama interface implementations)
• Direct franz-go API usage instead of abstraction layers
• Consumer/producer code is cleaner and more maintainable

Code Quality:

• Test updates properly reflect new message structure (removed Sarama wrapper)
• Error handling maintained throughout
• TLS configuration properly migrated
• Watchdog and health check logic preserved