feat: add modern web UI with React and real-time updates (PR #38)

Implements Agent A's v0.9.0 Web UI features:

- Modern React web UI with TypeScript and Vite
- Real-time WebSocket updates
- Interactive resource graph visualization
- Dark mode support
- Responsive design
- Static assets embedded in Go binary
- CLI commands: simctl ui serve, simctl ui build

All CI checks passing. Includes 9 commits with comprehensive fixes and improvements.

Co-authored-by: Agent A <agent-a@v0.9.0>