docs: Complete README rewrite with architecture diagrams and full capability map

- ASCII architecture diagram (UI, core engine, integration, system layers)
- Nova API server endpoint table with curl examples
- Full feature breakdown (scanning, AI/ML, security, compliance, UniFi)
- Installation, build, and usage instructions
- Version history, project structure, security section

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kochj23