feat(blog): add the blog index, post pages, RSS and content sitemap

The rendering split is dictated by CI building with no database.

/blog, /blog/rss.xml and /content-sitemap.xml have no dynamic params, so
Next prerenders them at build time and the build fails on a missing
Payload secret — caught here, not on staging. They are force-dynamic
instead: one indexed query against Postgres on the same Docker network,
and a newly published post appears immediately rather than waiting on a
revalidation. /blog/[slug] keeps ISR, because with no
generateStaticParams there is nothing to prerender; it is generated on
first request and cached, which is exactly what the collection's
afterChange hook exists to invalidate.

RichText takes `converters`, not `blocks`, in Payload 3.88, and the
default converters must be spread or every paragraph and heading loses
its renderer and the body comes out empty.

BlogPosting references the Person and Organization by @id rather than
repeating them, so every post and the About page resolve to one author
entity instead of declaring several people with the same name.

/sitemap.xml is proxied from FastAPI, which knows nothing about Payload,
so the Next-owned URLs get their own sitemap and robots.txt lists both.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017YmbBhr8s7GusjDE12hrZM

nextjs-app/__tests__/app/blogMetadata.test.ts

@@ -0,0 +1,53 @@
+/**
+ * The blog index imports getCachedPayload, which pulls in Payload — ESM-only,
+ * and next/jest will not transform node_modules. Mocking that one module keeps
+ * the page's metadata testable without loading the CMS; the mock is never
+ * called, because `metadata` is a static export evaluated at import time.
+ */
+jest.mock('@/lib/payload', () => ({ getCachedPayload: jest.fn() }));
+
+import { metadata } from '@/app/(frontend)/blog/page';
+import { blogPostingJsonLd, breadcrumbJsonLd } from '@/lib/jsonld';
+
+const post = {
+  title: 'What the data cannot tell you',
+  slug: 'what-the-data-cannot-tell-you',
+  excerpt: 'Results describe one year group on a handful of days.',
+  publishedAt: '2026-09-15T00:00:00.000Z',
+};
+
+describe('/blog metadata', () => {
+  it('canonicalises to the bare path', () => {
+    expect(metadata.alternates?.canonical)
+      .toBe('https://www.schoolcompare.co.uk/blog');
+  });
+});
+
+describe('BlogPosting structured data', () => {
+  it('names the same Person entity the about page declares', () => {
+    // By @id, not by repeating the person: search engines must resolve every
+    // post and the about page to one author entity, or the site has several.
+    const ld = blogPostingJsonLd(post);
+    expect(ld['@type']).toBe('BlogPosting');
+    expect(ld.author['@id']).toBe('https://www.schoolcompare.co.uk/about#tudor');
+    expect(ld.publisher['@id']).toBe('https://www.schoolcompare.co.uk#organization');
+  });
+
+  it('carries a self-referencing canonical url and the publish date', () => {
+    const ld = blogPostingJsonLd(post);
+    expect(ld.url).toBe(
+      'https://www.schoolcompare.co.uk/blog/what-the-data-cannot-tell-you',
+    );
+    expect(ld.datePublished).toBe('2026-09-15T00:00:00.000Z');
+  });
+});
+
+describe('breadcrumbs', () => {
+  it('places the post under the blog index', () => {
+    const ld = breadcrumbJsonLd(post);
+    expect(ld.itemListElement[0].item).toBe('https://www.schoolcompare.co.uk/blog');
+    expect(ld.itemListElement[1].item).toBe(
+      'https://www.schoolcompare.co.uk/blog/what-the-data-cannot-tell-you',
+    );
+  });
+});

nextjs-app/__tests__/app/robots.test.ts

@@ -9,3 +9,12 @@ describe('robots.txt', () => {
     );
   });
 });
+
+describe('sitemap discovery', () => {
+  it('lists both the proxied school sitemap and the Next-owned content sitemap', () => {
+    expect(robots().sitemap).toEqual([
+      'https://www.schoolcompare.co.uk/sitemap.xml',
+      'https://www.schoolcompare.co.uk/content-sitemap.xml',
+    ]);
+  });
+});

nextjs-app/__tests__/payload/collections.test.ts

@@ -33,13 +33,13 @@ describe('posts collection', () => {
     expect(POSTS).toMatch(/access:\s*\{\s*read:\s*\(\)\s*=>\s*true/);
   });
 
-  it('revalidates the blog paths when a post changes or is deleted', () => {
-    // Blog pages are ISR because CI builds with no database. Without these
-    // hooks a published post would not appear until the revalidate window
-    // expired — up to an hour of a writer thinking publishing is broken.
+  it('revalidates the post page when a post changes or is deleted', () => {
+    // /blog/[slug] is ISR — generated on first request and cached — so an edit
+    // to an already-published post would otherwise not appear until the
+    // revalidate window expired, up to an hour of a writer concluding that
+    // saving is broken. The index and feeds are force-dynamic and need no hook.
     expect(POSTS).toContain('afterChange');
     expect(POSTS).toContain('afterDelete');
-    expect(POSTS).toMatch(/revalidatePath\('\/blog'\)/);
     expect(POSTS).toMatch(/revalidatePath\(`\/blog\/\$\{[^}]+\}`\)/);
   });
 });