• Add Kafka client for sending relay metrics to external systems
• Implement retry logic with exponential backoff for Kafka send failures
• Add retry queue to handle persistent failures and prevent data loss
• Add proper error handling and monitoring for Kafka connectivity issues
• Integrate Kafka client into RPC consumer metrics pipeline
• Add command-line flag --relay-kafka-address for Kafka configuration
• Support Kafka topic configuration via --relay-kafka-topic flag
• Add unit tests for Kafka client functionality
• Update go.mod and go.sum with Kafka dependencies

This enables reliable delivery of relay metrics to Kafka for external monitoring and analytics, with robust error handling and retry mechanisms.

Description

Closes: #XXXX

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