test: add comprehensive automated test coverage

- Vitest multi-project setup (unit / integration / component)
- Real-Postgres integration harness via in-process PGlite (TEST_DATABASE_URL
  override), migrations applied per worker; production code untouched
- Unit: routing, locale, validation/Zod schemas, metadata, mail, site-theme,
  marquee, media, portfolio helpers, plus architecture-rule tests
- Integration: Prisma data layer, API routes, and all server actions
- Component: UI primitives and form components (jsdom + Testing Library)
- 371 tests passing

tests/integration/api-routes.test.ts

@@ -0,0 +1,52 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { GET as healthGet } from "@/app/api/health/route";
+import { GET as defaultLocaleGet } from "@/app/api/site/default-locale/route";
+import { setMaintenanceMode, updateSiteSettings, getSiteSettings } from "@/lib/app-config";
+import { prisma } from "@/lib/prisma";
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+describe("GET /api/health", () => {
+  it("reports ok when the database responds", async () => {
+    const response = await healthGet();
+    expect(response.status).toBe(200);
+    const body = await response.json();
+    expect(body.status).toBe("ok");
+    expect(body.checks.database).toBe("up");
+    expect(typeof body.timestamp).toBe("string");
+  });
+
+  it("reports degraded (503) when the database query throws", async () => {
+    vi.spyOn(prisma, "$queryRaw").mockRejectedValueOnce(new Error("db down"));
+    const response = await healthGet();
+    expect(response.status).toBe(503);
+    const body = await response.json();
+    expect(body.status).toBe("degraded");
+    expect(body.checks.database).toBe("down");
+  });
+});
+
+describe("GET /api/site/default-locale", () => {
+  it("returns the runtime default locale and maintenance flag with no-store", async () => {
+    const response = await defaultLocaleGet();
+    expect(response.headers.get("Cache-Control")).toBe("no-store, max-age=0");
+    const body = await response.json();
+    expect(body.defaultLocale).toBe("de");
+    expect(body.maintenanceEnabled).toBe(false);
+  });
+
+  it("reflects updated settings and maintenance state", async () => {
+    const settings = await getSiteSettings();
+    settings.defaultLocale = "ar";
+    await updateSiteSettings(settings);
+    await setMaintenanceMode(true);
+
+    const response = await defaultLocaleGet();
+    const body = await response.json();
+    expect(body.defaultLocale).toBe("ar");
+    expect(body.maintenanceEnabled).toBe(true);
+  });
+});