Restructure UI: three-column layout with left nav and right sidebar

- Left nav: Orders / About sections
- Right sidebar: chaos mode toggle, DLQ auto-resume, API endpoint
- About section: architecture diagram, service breakdown, chaos walkthrough
- Chaos mode toggle directly calls LocalStack chaos API from the browser

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: whummer