Integrate BullMQ Job Queue

[mijinummi]

🧠 Concept

Support asynchronous event processing.

⚠️ Problem

Heavy workloads should not block API requests.

📁 Implementation Scope

• src/modules/queues/

✅ Requirements

• Queue setup
• Worker registration
• Retry policies

🎯 Acceptance Criteria

• BullMQ configured
• Jobs processed
• Retry support enabled