feat: add ECS logging support with unified message field

- Add pino and @elastic/ecs-pino-format dependencies
- Create logger module with dev/prod configurations
- Update all logging to use message field consistently
- Add getStage() function for environment management
- Remove console.log statements
- Add comprehensive unit tests for logger module
- Achieve 96% code coverage

All new services from this template will have:
- ECS-compliant logging
- Pretty dev logs, JSON prod logs
- Unified message field
- Clean Elasticsearch/Kibana integration

Author: charlypa