Rebuild atomcms-next foundation on Prisma (align to habbo-next reference)

Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7
data layer, mirroring the proven habbo-next approach to the shared Arcturus
emulator DB (introspect/conform only, idempotent SQL migrations via a custom
runner; never migrate-diff).

- prisma/schema.prisma: User, UsersCurrency (composite PK), Ban, WebsiteSetting
  mapped to AtomCMS's default.sql columns; client generated to src/generated/prisma
- src/lib/prisma.ts: PrismaMariaDb adapter singleton; src/env.ts zod env
- src/lib/services: siteSettings (cached setting() equivalent) + CurrencyType enum
- prisma/migrations + scripts/apply-migrations.ts: idempotent CMS-table runner

Verified: prisma generate OK, tsc --noEmit exit 0, vitest 6/6 pass.

.gitignore

@@ -1,5 +1,6 @@
 node_modules/
-dist/
 .turbo/
 .env
 *.tsbuildinfo
+# Prisma client is generated by `prisma generate`
+src/generated/