- Update fetch_config to use protobuf instead of JSON
- Add conversion functions from protobuf types to internal config types
- Update heartbeat to use protobuf encoding
- All API endpoints now use Protocol Buffers (config, metrics, heartbeat)
- Reduces 7 unused struct warnings to 1 (HeartbeatResponse)
- Change registry from GitLab to Docker Hub (gmcintire/towerops-agent)
- Update authentication to use DOCKERHUB_USERNAME and DOCKERHUB_TOKEN
- Remove vntx runner tags to use GitLab shared runners