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/component/_smoke.test.tsx

@@ -0,0 +1,11 @@
+import { render, screen } from "@testing-library/react";
+import { describe, expect, it } from "vitest";
+
+import { Badge } from "@/components/ui/badge";
+
+describe("component harness smoke test", () => {
+  it("renders a component into jsdom", () => {
+    render(<Badge>Hello</Badge>);
+    expect(screen.getByText("Hello")).toBeInTheDocument();
+  });
+});