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/helpers/integration-setup.ts

@@ -0,0 +1,69 @@
+import { readFileSync, readdirSync } from "fs";
+import path from "path";
+
+import { afterAll, beforeEach, vi } from "vitest";
+
+/**
+ * Integration database wiring.
+ *
+ *  - If TEST_DATABASE_URL is set, the real `lib/prisma` singleton is used unchanged,
+ *    pointed at that Postgres (e.g. the Docker instance). Migrations are applied once
+ *    by the global setup; files run serially and truncate between tests.
+ *
+ *  - Otherwise, `lib/prisma` is mocked with a Prisma client backed by an in-process
+ *    PGlite database (Postgres compiled to WASM) — real Postgres semantics, fully
+ *    isolated per worker, no external server. Production code is never modified.
+ */
+
+const realDbUrl = process.env.TEST_DATABASE_URL?.trim();
+if (realDbUrl) {
+  process.env.DATABASE_URL = realDbUrl;
+}
+
+vi.mock("@/lib/prisma", async () => {
+  if (process.env.TEST_DATABASE_URL?.trim()) {
+    return await vi.importActual<typeof import("@/lib/prisma")>("@/lib/prisma");
+  }
+
+  const { PGlite } = await import("@electric-sql/pglite");
+  const { PrismaPGlite } = await import("pglite-prisma-adapter");
+  const { PrismaClient } = await import("@prisma/client");
+
+  const db = await PGlite.create();
+  const migrationsDir = path.resolve(process.cwd(), "prisma", "migrations");
+  const dirs = readdirSync(migrationsDir)
+    .filter((entry) => /^\d/.test(entry))
+    .sort();
+  for (const dir of dirs) {
+    await db.exec(readFileSync(path.join(migrationsDir, dir, "migration.sql"), "utf8"));
+  }
+
+  const prisma = new PrismaClient({ adapter: new PrismaPGlite(db) });
+  return { prisma };
+});
+
+const { prisma } = await import("@/lib/prisma");
+
+// Truncated in dependency order (children first) between every test for isolation.
+const TABLES = [
+  "MediaUsage",
+  "MediaAsset",
+  "PortfolioAsset",
+  "PortfolioSection",
+  "PortfolioProject",
+  "Category",
+  "AppConfig",
+];
+
+export async function resetDb() {
+  const list = TABLES.map((table) => `"${table}"`).join(", ");
+  await prisma.$executeRawUnsafe(`TRUNCATE TABLE ${list} RESTART IDENTITY CASCADE;`);
+}
+
+beforeEach(async () => {
+  await resetDb();
+});
+
+afterAll(async () => {
+  await prisma.$disconnect();
+});