Add NestJS-based orchestrator service structure for M6-AgentOrchestration.
Changes:
- Migrate from Express to NestJS architecture
- Add health check endpoint module
- Add placeholder modules: coordinator, git, killswitch, monitor, queue, spawner, valkey
- Update configuration for NestJS
- Update lockfile for new dependencies
This is foundational work for M6-AgentOrchestration milestone.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
