refactor(app): move site routes into a (frontend) route group

Payload's admin panel ships its own root layout rendering html/body.
Next allows multiple root layouts only when no app/layout.tsx exists, so
the site's routes move into their own group. Route groups are invisible
to routing: every public URL is unchanged, verified against the build's
route table.

The metadata file conventions deliberately stay at the app/ root. Moving
them into the group renamed /icon.png to /icon-4usi79.png (likewise
apple-icon and opengraph-image) and dropped /robots.txt altogether,
which would have broken the /icon.png cache-control rule, the
outputFileTracingIncludes entry for the share card, and robots.txt.

darkThemeSafety reads app/globals.css off disk rather than importing it,
so it needed its own path fix — a grep for import specifiers misses it,
and it fails as an unrunnable suite rather than a failed assertion.

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

nextjs-app/app/(frontend)/schools/authority/[la]/[phase]/page.tsx

@@ -0,0 +1,65 @@
+/**
+ * Phase variants of an authority page.
+ *
+ * The spec called for these; the plan built the bare authority route and
+ * dropped them. Nothing caught it, because the sitemap is written from the
+ * place registry — which was right about them all along — while the routes
+ * were written by hand. 302 authority phase URLs were submitted to Google and
+ * every one 404'd, and every authority page linked to a phase page in the
+ * *town* namespace, which is a different set of schools entirely.
+ *
+ * "Primary schools in Kent" is the query these serve, and it is a real one:
+ * admissions are authority-run, so the authority is the unit a parent thinks
+ * in when they have not settled on a town.
+ */
+import { notFound } from 'next/navigation';
+import type { Metadata } from 'next';
+import { fetchPlace } from '@/lib/places';
+import { fetchNationalAverages } from '@/lib/api';
+import { PlaceView } from '@/components/places/PlaceView';
+import { absoluteUrl } from '@/lib/site';
+
+interface Props { params: Promise<{ la: string; phase: string }> }
+
+export const revalidate = 604800;
+export const dynamicParams = true;
+
+const PHASES = ['primary', 'secondary'] as const;
+type Phase = (typeof PHASES)[number];
+
+const isPhase = (v: string): v is Phase => (PHASES as readonly string[]).includes(v);
+
+export async function generateMetadata({ params }: Props): Promise<Metadata> {
+  const { la, phase } = await params;
+  if (!isPhase(phase)) return { title: 'Place Not Found' };
+  const detail = await fetchPlace('authority', la, phase);
+  if (!detail || detail.schools.length === 0) return { title: 'Place Not Found' };
+
+  const word = phase === 'secondary' ? 'Secondary' : 'Primary';
+  const { name } = detail.place;
+  return {
+    // "Local Authority" stays in the title for the same reason it is on the
+    // bare authority page: 67 town names collide with an authority name, and
+    // a reader landing on both needs to know which set each covers.
+    title: { absolute: `${word} Schools in ${name} — Local Authority | schoolcompare` },
+    description:
+      `Every ${phase} school in the ${name} local authority, with results, Ofsted `
+      + `grades and the authority average against England.`,
+    alternates: { canonical: absoluteUrl(`/schools/authority/${la}/${phase}`) },
+  };
+}
+
+export default async function AuthorityPhasePage({ params }: Props) {
+  const { la, phase } = await params;
+  if (!isPhase(phase)) notFound();
+  const detail = await fetchPlace('authority', la, phase);
+  if (!detail || detail.schools.length === 0) notFound();
+
+  const national = await fetchNationalAverages().catch(() => null);
+  const englandAverage = phase === 'secondary'
+    ? national?.secondary?.attainment_8_score ?? null
+    : national?.primary?.rwm_expected_pct ?? null;
+
+  return <PlaceView detail={detail} phase={phase}
+    englandAverage={englandAverage} neighbours={[]} />;
+}

nextjs-app/app/(frontend)/schools/authority/[la]/page.tsx

@@ -0,0 +1,67 @@
+/**
+ * Local authority pages.
+ *
+ * A separate namespace from /schools/[place] because 67 town names collide
+ * with an authority name and neither set contains the other — Bedford the
+ * town holds 104 schools, Bedford the authority 86, because postal towns
+ * cross authority boundaries. The title says "Local Authority" so a reader
+ * landing on both knows which set each covers.
+ */
+import { notFound } from 'next/navigation';
+import type { Metadata } from 'next';
+import { fetchPlace, fetchPlaces } from '@/lib/places';
+import { fetchNationalAverages } from '@/lib/api';
+import { PlaceView } from '@/components/places/PlaceView';
+import { absoluteUrl } from '@/lib/site';
+
+interface Props { params: Promise<{ la: string }> }
+
+export const revalidate = 604800;
+export const dynamicParams = true;
+
+export async function generateStaticParams(): Promise<Array<{ la: string }>> {
+  // Gated like every other prerender in this app. There are only ~154
+  // authorities, but "few enough to always build" still means the API must be
+  // reachable at build time, and in CI it is not — the build fails with
+  // ECONNREFUSED rather than degrading. The catch is the same fallback the
+  // school route uses.
+  if (process.env.PRERENDER_PLACES !== '1') return [];
+  try {
+    return (await fetchPlaces())
+      .filter((p) => p.kind === 'authority')
+      .map((p) => ({ la: p.slug }));
+  } catch (error) {
+    console.warn('generateStaticParams: API unreachable, falling back to on-demand ISR.', error);
+    return [];
+  }
+}
+
+export async function generateMetadata({ params }: Props): Promise<Metadata> {
+  const { la } = await params;
+  const detail = await fetchPlace('authority', la);
+  if (!detail) return { title: 'Place Not Found' };
+
+  const { name, count } = detail.place;
+  return {
+    title: { absolute: `Schools in ${name} — Local Authority | schoolcompare` },
+    description:
+      `All ${count} schools in the ${name} local authority, with SATs and GCSE results, `
+      + `Ofsted grades and the authority average against England.`,
+    alternates: { canonical: absoluteUrl(`/schools/authority/${la}`) },
+  };
+}
+
+export default async function AuthorityPage({ params }: Props) {
+  const { la } = await params;
+  const detail = await fetchPlace('authority', la);
+  if (!detail) notFound();
+
+  const national = await fetchNationalAverages().catch(() => null);
+  return (
+    <PlaceView
+      detail={detail}
+      englandAverage={national?.primary?.rwm_expected_pct ?? null}
+      neighbours={[]}
+    />
+  );
+}