feat(features): add test factories to all 5 features

Adds src/__factories__/<entity>.factory.ts to auth, blog, marketing-pages,
navigation, media. Each factory uses defineFactory from @repo/core-testing
with stable date defaults (2026-01-01) so snapshot diffs reflect SUT
behavior only. Refactors mechanical inline-fixture tests to use factories.

Also adds vitest.config.ts and tsconfig path alias to @repo/media (lacked
both), and adds @repo/core-testing devDependency to @repo/media.

Spec: §5.1, §6.3

packages/marketing-pages/src/__factories__/index.ts

@@ -0,0 +1,2 @@
+export { pageFactory } from "./page.factory.js";
+export { siteSettingsFactory } from "./site-settings.factory.js";

packages/marketing-pages/src/__factories__/page.factory.test.ts

@@ -0,0 +1,29 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { pageFactory } from "@/__factories__/page.factory";
+
+describe("pageFactory", () => {
+  beforeEach(() => pageFactory.reset());
+
+  it("returns a Page with stable defaults", () => {
+    const p = pageFactory.build();
+    expect(p.id).toBe("page-1");
+    expect(p.title).toBe("Page 1");
+    expect(p.slug).toBe("page-1");
+    expect(p.status).toBe("draft");
+    expect(p.createdAt).toEqual(new Date("2026-01-01T00:00:00Z"));
+  });
+
+  it("applies overrides", () => {
+    const p = pageFactory.build({ status: "published", title: "About" });
+    expect(p.status).toBe("published");
+    expect(p.title).toBe("About");
+    expect(p.id).toBe("page-1");
+  });
+
+  it("increments sequence per build", () => {
+    const a = pageFactory.build();
+    const b = pageFactory.build();
+    expect(a.id).toBe("page-1");
+    expect(b.id).toBe("page-2");
+  });
+});

packages/marketing-pages/src/__factories__/page.factory.ts

@@ -0,0 +1,19 @@
+import { defineFactory } from "@repo/core-testing/factory";
+import type { Page } from "../entities/page.js";
+
+export const pageFactory = defineFactory<Page>(({ sequence }) => ({
+  id: `page-${sequence}`,
+  title: `Page ${sequence}`,
+  slug: `page-${sequence}`,
+  hero: {
+    heading: `Hero ${sequence}`,
+  },
+  layout: [],
+  status: "draft",
+  publishedAt: null,
+  seo: {
+    title: `Page ${sequence} | Site`,
+  },
+  createdAt: new Date("2026-01-01T00:00:00Z"),
+  updatedAt: new Date("2026-01-01T00:00:00Z"),
+}));

packages/marketing-pages/src/__factories__/site-settings.factory.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { siteSettingsFactory } from "@/__factories__/site-settings.factory";
+
+describe("siteSettingsFactory", () => {
+  beforeEach(() => siteSettingsFactory.reset());
+
+  it("returns SiteSettings with stable defaults", () => {
+    const s = siteSettingsFactory.build();
+    expect(s.siteName).toBe("Site 1");
+  });
+
+  it("applies overrides", () => {
+    const s = siteSettingsFactory.build({ siteName: "My Brand" });
+    expect(s.siteName).toBe("My Brand");
+  });
+
+  it("increments sequence per build (siteName reflects it)", () => {
+    const a = siteSettingsFactory.build();
+    const b = siteSettingsFactory.build();
+    expect(a.siteName).toBe("Site 1");
+    expect(b.siteName).toBe("Site 2");
+  });
+});

packages/marketing-pages/src/__factories__/site-settings.factory.ts

@@ -0,0 +1,6 @@
+import { defineFactory } from "@repo/core-testing/factory";
+import type { SiteSettings } from "../entities/site-settings.js";
+
+export const siteSettingsFactory = defineFactory<SiteSettings>(({ sequence }) => ({
+  siteName: `Site ${sequence}`,
+}));