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/unit/admin-feedback.test.ts

@@ -0,0 +1,36 @@
+import { describe, expect, it } from "vitest";
+
+import { readFlash, withFlash } from "@/lib/admin-feedback";
+
+describe("withFlash", () => {
+  it("returns the plain path when there are no messages", () => {
+    expect(withFlash("/admin/smtp", {})).toBe("/admin/smtp");
+  });
+
+  it("appends a success message", () => {
+    expect(withFlash("/admin/smtp", { success: "Saved." })).toBe("/admin/smtp?success=Saved.");
+  });
+
+  it("appends an error message", () => {
+    expect(withFlash("/admin/smtp", { error: "Nope." })).toBe("/admin/smtp?error=Nope.");
+  });
+
+  it("appends both and url-encodes values", () => {
+    const result = withFlash("/admin/smtp", { success: "a b", error: "x&y" });
+    const params = new URL(result, "http://local").searchParams;
+    expect(params.get("success")).toBe("a b");
+    expect(params.get("error")).toBe("x&y");
+  });
+});
+
+describe("readFlash", () => {
+  it("reads success and error from resolved search params", () => {
+    expect(readFlash({ success: "ok", error: "bad" })).toEqual({ success: "ok", error: "bad" });
+  });
+
+  it("returns undefined fields when params are missing", () => {
+    expect(readFlash(undefined)).toEqual({ success: undefined, error: undefined });
+    expect(readFlash(null)).toEqual({ success: undefined, error: undefined });
+    expect(readFlash({})).toEqual({ success: undefined, error: undefined });
+  });
+});