Five-section front door for new contributors: product description,
subsystem map, quick-start (local dev + full Docker variant), where-to-go-next
with TODO markers for DOC-2/4/5, and one-line private license.
Corrects stale port reference (3000→5173, per vite.config.ts).
Links docs/GLOSSARY.md, docs/adr/, docs/architecture/c4-diagrams.md,
and Gitea issue tracker with LAN qualifier.
Closes#395
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
