Log RabbitMQ dead-letter decisions before publication

[KilianBoute]

Summary

Add optional RabbitOptions.SetLogger using the existing service logrus logger and models/pkg/api envelope. Emit one WARN dead_letter_requested before attempting a new DLQ publication.

Reuse the existing DeadLetterReason catalog: malformed, handler_error, retry_exhausted, publish_failed and unspecified. Include source/DLQ queue, attempts and already-decoded event traceId/media filename where available.

• No new failure metadata, headers, message-handler signature or envelope schema.
• No additional payload/envelope decoding, observer registration, async worker or buffer.
• No decision log on normal forwards, cancellation, retries below the cap, or administrative scan/replay restoration.
• No claim that publication succeeded; logs describe the decision, not delivery.
• Existing acknowledgement, recovery and publishing behavior is unchanged.

Validation

• GOWORK=off GOTOOLCHAIN=auto go test -race ./pkg/queue -count=1 -timeout=120s
• GOWORK=off GOTOOLCHAIN=auto go vet ./pkg/queue
• Sequence integration race tests and vet passed against this implementation.
• Tests verify catalog/status fields, safe correlation, prepublish ordering, disabled logging, terminal vs nonterminal actions, unchanged payloads/settlement, and administrative exclusions.

Supersedes the diagnostic infrastructure approach in closed uug-ai/hub-pipeline-sequence#92. Existing optional DLQ observer remains available but is not needed or enabled by this approach.

[codecov]

Codecov Report

❌ Patch coverage is 67.32673% with 33 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pkg/queue/rabbitmq.go	57.14%	23 Missing and 10 partials ⚠️

📢 Thoughts on this report? Let us know!