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Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7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/migrations/0001_create_website_settings.sql

@@ -0,0 +1,10 @@
+-- CMS-owned settings table. Idempotent: safe to re-run.
+-- Mirrors AtomCMS's Laravel `website_settings` (key UNIQUE, value TEXT).
+CREATE TABLE IF NOT EXISTS website_settings (
+  id      BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+  `key`   VARCHAR(255) NOT NULL,
+  value   TEXT NOT NULL,
+  comment VARCHAR(255) NULL,
+  PRIMARY KEY (id),
+  UNIQUE KEY website_settings_key_unique (`key`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;