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Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7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.

.env.example

@@ -1,3 +1,11 @@
-# Connection to the LIVE/COPY emulator MySQL database (introspect-only).
-# Format: mysql://user:password@host:3306/database
-DATABASE_URL=
+# Connection to the LIVE/COPY emulator MySQL/MariaDB database.
+# The schema is owned by the Arcturus emulator — this app reads/writes data,
+# it does NOT own or migrate the emulator tables. Format:
+DATABASE_URL=mysql://user:[email protected]:3306/atomcms
+
+# Optional pool tuning (defaults shown)
+DATABASE_POOL_SIZE=40
+DATABASE_IDLE_TIMEOUT_MS=300000
+
+# Used by SSO ticket generation ({HOTEL_NAME}-{uuid})
+HOTEL_NAME=Atom