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)/compare/page.tsx

@@ -0,0 +1,95 @@
+/**
+ * Compare Page (SSR)
+ * Side-by-side comparison of schools with metrics
+ */
+
+import { fetchComparison, fetchMetrics } from '@/lib/api';
+import { ComparisonView } from '@/components/ComparisonView';
+import { absoluteUrl } from '@/lib/site';
+import type { Metadata } from 'next';
+
+interface ComparePageProps {
+  searchParams: Promise<{
+    urns?: string;
+    metric?: string;
+  }>;
+}
+
+/**
+ * Indexability depends on the query string, so this cannot be a static export.
+ *
+ * Bare /compare is the landing page for the "compare schools" head term and
+ * stays indexable. /compare?urns=… is an unbounded parameter space — 25,193
+ * schools make ~317 million pairs — so it goes noindex. It stays `follow` and
+ * keeps a canonical to the bare path, so the links out to each school page
+ * still count.
+ */
+export async function generateMetadata(
+  { searchParams }: ComparePageProps,
+): Promise<Metadata> {
+  const { urns } = await searchParams;
+
+  const base: Metadata = {
+    // Deliberately not the homepage's phrase. Two pages chasing "compare
+    // schools" is how a site competes with itself; this one takes the tool
+    // phrasing instead.
+    title: 'School Comparison Tool — Up to Five at Once | schoolcompare',
+    description:
+      'Put up to five English schools in one table: SATs and GCSE results against the England average, Ofsted grades, and the distance places were offered.',
+    keywords:
+      'school comparison, compare schools, Ofsted comparison, school admissions, KS2 comparison, primary school performance',
+    alternates: { canonical: absoluteUrl('/compare') },
+  };
+
+  if (!urns) return base;
+
+  return { ...base, robots: { index: false, follow: true } };
+}
+
+// Dynamic via searchParams; remove force-dynamic so internal data fetches
+// can still use Next.js's per-call revalidate cache.
+
+export default async function ComparePage({ searchParams }: ComparePageProps) {
+  const { urns: urnsParam, metric: metricParam } = await searchParams;
+
+  const urns = urnsParam?.split(',').map(Number).filter(Boolean) || [];
+  const selectedMetric = metricParam || 'rwm_expected_pct';
+
+  try {
+    // Fetch comparison + metrics in parallel — they are independent.
+    const [comparisonResponse, metricsResponse] = await Promise.all([
+      urns.length > 0
+        ? fetchComparison(urnsParam!).catch((error) => {
+            console.error('Failed to fetch comparison:', error);
+            return null;
+          })
+        : Promise.resolve(null),
+      fetchMetrics(),
+    ]);
+
+    const metricsArray = metricsResponse?.metrics || [];
+
+    return (
+      <ComparisonView
+        initialData={comparisonResponse?.comparison ?? null}
+        initialNationalAverages={comparisonResponse?.national_averages}
+        initialBenchmarks={comparisonResponse?.benchmarks}
+        initialUrns={urns}
+        metrics={metricsArray}
+        selectedMetric={selectedMetric}
+      />
+    );
+  } catch (error) {
+    console.error('Error fetching data for compare page:', error);
+
+    // Return error state with empty metrics
+    return (
+      <ComparisonView
+        initialData={null}
+        initialUrns={urns}
+        metrics={[]}
+        selectedMetric={selectedMetric}
+      />
+    );
+  }
+}