feat: implement Dead Letter Queue (DLQ)

[LeonardoVieira1630]

📘 Context

Currently, when the system encounters a message it cannot process (e.g., unknown trigger), it enters an infinite reprocessing loop due to NACK with requeue. This causes:

• High redelivery rate (200+ messages/second)
• Blocking of other messages in the queue (prefetch=1)
• Unnecessary resource consumption
• Inability to process valid messages

🐞 Problem Identified

During an accidental deployment of development code to production, voting-power-changed messages were generated. When production code was restored, these messages got stuck in the queue causing an infinite loop, as the dispatcher doesn't have a handler for this trigger type.

🔧 Tasks

1. Update RabbitMQConsumer to automatically create DLQ

   • Modify consumer.ts to configure DLQ for all queues
   • Configure queue with x-dead-letter-exchange and x-dead-letter-routing-key
   • Automatically create DLQ with .dlq suffix
   • Set 7-day TTL for messages in DLQ

2. Implement retry logic with counter

   • Add x-retry-count header to messages
   • After 3 attempts, use channel.reject(msg, false) to send to DLQ
   • Include error information in message header

3. Add default handler for unknown triggers

   • Warning log for unregistered trigger
   • Direct ACK after logging (don't send to DLQ)

4. Create monitoring script

   • Script to check messages in DLQs
   • Prepare structure for n8n integration

5. Tests

   • Unit test for retry behavior
   • Integration test with unknown trigger message
   • Verify messages go to DLQ after 3 attempts