Add redis (Cache + queue)

Integrate Redis for caching and job queueing.

**Requirements:**
- Setup Redis instance (local or cloud)
- Create cache service for frequently accessed data (user profiles, groups, etc.)
- Implement session management with Redis
- Add job queue functionality using Bull or similar
- Configure cache invalidation strategies
- Add monitoring and health checks for Redis

**Deliverables:**
- Redis connection service
- Cache service module with get/set/delete operations
- Session management implementation
- Job queue setup and handlers
- Redis configuration and documentation