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/site-theme.test.ts

@@ -0,0 +1,53 @@
+import { describe, expect, it } from "vitest";
+
+import { buildSiteThemeStyleText, buildSiteThemeTokens } from "@/lib/site-theme";
+
+const CHANNEL = /^\d+ \d+% \d+%$/;
+
+describe("buildSiteThemeTokens", () => {
+  it("converts pure red to the expected HSL channels", () => {
+    const tokens = buildSiteThemeTokens("#ff0000");
+    expect(tokens.light.primary).toBe("0 100% 50%");
+    // dark primary lightens by 6 and clamps saturation into [40,95]
+    expect(tokens.dark.primary).toBe("0 95% 56%");
+  });
+
+  it("produces zero saturation for a neutral gray", () => {
+    const tokens = buildSiteThemeTokens("#808080");
+    expect(tokens.light.primary.startsWith("0 0%")).toBe(true);
+  });
+
+  it("emits well-formed channel strings for every token", () => {
+    const tokens = buildSiteThemeTokens("#dc5a35");
+    for (const value of [
+      tokens.light.primary,
+      tokens.light.secondary,
+      tokens.dark.primary,
+      tokens.dark.secondary,
+    ]) {
+      expect(value).toMatch(CHANNEL);
+    }
+  });
+
+  it("derives distinct dark and secondary variants", () => {
+    const tokens = buildSiteThemeTokens("#dc5a35");
+    expect(tokens.dark.primary).not.toBe(tokens.light.primary);
+    expect(tokens.light.secondary).not.toBe(tokens.light.primary);
+  });
+
+  it("falls back to the default brand color for invalid input", () => {
+    expect(buildSiteThemeTokens("not-a-color")).toEqual(buildSiteThemeTokens("#dc5a35"));
+    expect(buildSiteThemeTokens("")).toEqual(buildSiteThemeTokens("#dc5a35"));
+  });
+});
+
+describe("buildSiteThemeStyleText", () => {
+  it("emits :root and .dark blocks with the derived channels", () => {
+    const css = buildSiteThemeStyleText("#ff0000");
+    expect(css).toContain(":root {");
+    expect(css).toContain(".dark {");
+    expect(css).toContain("--primary: 0 100% 50%;");
+    expect(css).toContain("--brand-secondary:");
+    expect(css).toContain("--sidebar-ring:");
+  });
+});