- Replace JSON file storage with PostgreSQL (pg package)
- Add db.ts service for connection pool and schema init
- Rewrite keys.ts, verification.ts, usage.ts for async PostgreSQL
- Update all routes for async function signatures
- Add migration script (scripts/migrate-to-postgres.mjs)
- Update docker-compose.yml with DATABASE_* env vars
- Change SLA from 99.9% to 99.5% in landing page