Adds comprehensive documentation for v0.5 release: deployment guide
covering Vercel/Netlify/self-hosted options, system architecture overview,
and code standards for theme development.
Improves onboarding and contribution experience.
Captures CSS specificity gotcha, Hugo jsonify-in-script trap, hardcoded SVG fill issue, and the modular-commit safety net learned from the same-day v0.1 → v0.2 cadence.