Polish public v0.1.0 presentation

[manishklach]

What changed

• Reworked the README into a polished public project landing page with badges, architecture, design thesis, reference hardware, validation status, and documentation map.
• Added a detailed v0.1.0 changelog.
• Added public contribution guidance and a security reporting policy.

Why

The repository is being published as the Phase 1 reference implementation for the low-cost ExpertMesh architecture and needs clear claims, boundaries, onboarding, and release documentation.

Validation

• pytest -q — 6 passed
• ruff check src tests — passed
• SVG XML validation — passed
• Secret-pattern scan — no matches
• git diff --check — passed