docs: add PR description for issues

[devpeter999]

Fix issues Closes #12, Closes #13, Closes #14, and Closes #16

All four issues have been resolved in this PR.

Summary

• Configure CORS #8 Configure CORS — Registered @fastify/cors with an env-driven origin allowlist (CORS_ORIGIN). Frontend can now call the API from its dev origin.
• Replace prisma db push with migrations #9 Replace prisma db push with migrations — Committed initial migration under prisma/migrations/. Both docker-compose.yml and scripts/dev.sh now run prisma migrate deploy instead of db push.
• Raise the declared Node version to 20.12 #10 Raise declared Node version to 20.12 — engines.node in package.json is now >=20.12. README updated to state the same minimum.
• Add a readiness endpoint that checks dependencies #11 Add a readiness endpoint — New /ready endpoint verifies database connectivity and reports indexer lag. Returns 503 when a dependency is unavailable.