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Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7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

prisma.config.ts

@@ -0,0 +1,16 @@
+import "dotenv/config";
+import { defineConfig, env } from "prisma/config";
+
+// Prisma 7 config. The datasource URL lives here (not in schema.prisma).
+// We NEVER run `prisma migrate`/`db push` against this database — it is shared
+// live with the Arcturus emulator. CMS-only schema changes go in
+// prisma/migrations/*.sql (idempotent) applied via `pnpm db:migrate`.
+export default defineConfig({
+  schema: "prisma/schema.prisma",
+  migrations: {
+    path: "prisma/migrations",
+  },
+  datasource: {
+    url: env("DATABASE_URL"),
+  },
+});