- Use @prisma/adapter-pg for PrismaClient (Prisma 7 removed datasourceUrl/datasources)
- prisma.config.ts: migrate.url for CLI commands
- schema.prisma: no url in datasource (Prisma 7 requirement)
- Add url = env("DATABASE_URL") back to schema (required by Prisma 7.5)
- Simplify prisma.config.ts
- First registered user auto-promoted to ADMIN via databaseHooks
- Subsequent users get HOST role