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Replace the superseded Drizzle monorepo scaffold with a single-app Prisma 7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/lib/services/site-settings.test.ts

@@ -0,0 +1,46 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const { findMany } = vi.hoisted(() => ({ findMany: vi.fn() }));
+vi.mock("@/lib/prisma", () => ({
+  prisma: { websiteSetting: { findMany } },
+}));
+
+import { siteSettings } from "./site-settings";
+
+beforeEach(() => {
+  findMany.mockReset();
+  siteSettings.reload();
+});
+
+describe("siteSettings", () => {
+  it("returns a value by key", async () => {
+    findMany.mockResolvedValue([{ key: "hotel_name", value: "AtomHotel" }]);
+    expect(await siteSettings.get("hotel_name")).toBe("AtomHotel");
+  });
+
+  it("returns the fallback when key is missing", async () => {
+    findMany.mockResolvedValue([]);
+    expect(await siteSettings.get("missing", "fallback")).toBe("fallback");
+    expect(await siteSettings.get("missing")).toBeNull();
+  });
+
+  it("coerces '1'/'0' string booleans", async () => {
+    findMany.mockResolvedValue([
+      { key: "maintenance_enabled", value: "1" },
+      { key: "radio_enabled", value: "0" },
+    ]);
+    expect(await siteSettings.getBool("maintenance_enabled")).toBe(true);
+    expect(await siteSettings.getBool("radio_enabled")).toBe(false);
+    expect(await siteSettings.getBool("missing", true)).toBe(true);
+  });
+
+  it("fetches once and caches until reload", async () => {
+    findMany.mockResolvedValue([{ key: "hotel_name", value: "AtomHotel" }]);
+    await siteSettings.get("hotel_name");
+    await siteSettings.getBool("hotel_name");
+    expect(findMany).toHaveBeenCalledTimes(1);
+    siteSettings.reload();
+    await siteSettings.get("hotel_name");
+    expect(findMany).toHaveBeenCalledTimes(2);
+  });
+});