- Add lib/db (schema, postgres.js client, enums, seed, migrations) on Drizzle
- Rewrite all lib and admin action queries from Prisma to Drizzle
- Keep existing table/column names so no data migration is needed
- Preserve signed-cookie admin auth unchanged
- Map unique-violation handling from Prisma P2002 to SQLSTATE 23505
- Swap deps, scripts, Makefile, and Dockerfile from Prisma to Drizzle
