Set up the foundation for Studio:
- Servant server on port 8090
- Shared layout with nav tabs: Agents | Memory | Notes | Tasks
- CSS based on Omni/Task/Web/Style.hs patterns
- Health endpoint at /health
- Create Omni/Agentd/Studio/Layout.hs for shared components
- Update Omni/Agentd/Studio.hs to use new layout