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Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7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

src/env.ts

@@ -0,0 +1,20 @@
+import { z } from "zod";
+
+// Minimal validated env for the foundation. When the Next.js app is added this
+// will move to @t3-oss/env-nextjs (the habbo-next pattern), but the data layer
+// only needs the DB connection + a couple of values today.
+const schema = z.object({
+  NODE_ENV: z.enum(["development", "test", "production"]).default("development"),
+  DATABASE_URL: z.string().url(),
+  DATABASE_POOL_SIZE: z.coerce.number().int().positive().default(40),
+  DATABASE_IDLE_TIMEOUT_MS: z.coerce.number().int().positive().default(300_000),
+  HOTEL_NAME: z.string().default("Atom"),
+});
+
+type Env = z.infer<typeof schema>;
+
+// SKIP_ENV_VALIDATION lets tooling (typecheck, tests that don't touch the DB)
+// import modules transitively without a populated .env.
+export const env: Env = process.env.SKIP_ENV_VALIDATION
+  ? (process.env as unknown as Env)
+  : schema.parse(process.env);