perf: cache aggressively and trim client bundle

Frontend
- Dynamic-import Chart.js components on detail/compare views so Chart.js
  no longer ships in initial JS.
- Drop force-dynamic on home, compare, rankings so internal data fetches
  reuse Next.js's per-call revalidate cache.
- Switch /school/[slug] to ISR with a 7-day revalidate window (school
  data updates annually).
- Preconnect to analytics + postcodes.io; remove redundant defer on the
  Umami Script tag (afterInteractive already covers it).
- Bump images.minimumCacheTTL to 1 year.
- Extract HowItWorks and Editorial sections as server components passed
  to HomeView via slot props so their JSX stays out of the client bundle.

Backend
- Add GZipMiddleware (min 512 bytes).
- Add CacheAndETagMiddleware: per-path Cache-Control with long s-maxage
  + stale-while-revalidate, ETag generation, and 304 on If-None-Match.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

nextjs-app/app/school/[slug]/page.tsx

@@ -4,13 +4,48 @@
  * URL format: /school/138267-school-name-here
  */
 
-import { fetchSchoolDetails } from '@/lib/api';
+import { fetchSchoolDetails, fetchSchools } from '@/lib/api';
 import { notFound, redirect } from 'next/navigation';
 import { SchoolDetailView } from '@/components/SchoolDetailView';
 import { SecondarySchoolDetailView } from '@/components/SecondarySchoolDetailView';
 import { parseSchoolSlug, schoolUrl } from '@/lib/utils';
 import type { Metadata } from 'next';
 
+/**
+ * Enumerate every school for static generation at build time.
+ *
+ * Set PRERENDER_SCHOOLS=1 in the build environment to enable. When disabled
+ * (or when the API can't be reached), we return an empty list and the route
+ * falls back to ISR on first request — `dynamicParams = true` covers it.
+ */
+export async function generateStaticParams(): Promise<Array<{ slug: string }>> {
+  if (process.env.PRERENDER_SCHOOLS !== '1') return [];
+
+  const params: Array<{ slug: string }> = [];
+  const PAGE_SIZE = 500;
+  let page = 1;
+  let totalPages = 1;
+
+  try {
+    do {
+      const res = await fetchSchools({ page, page_size: PAGE_SIZE });
+      for (const s of res.schools) {
+        const path = schoolUrl(s.urn, s.school_name);
+        const slug = path.replace('/school/', '');
+        params.push({ slug });
+      }
+      totalPages = res.total_pages || 1;
+      page += 1;
+    } while (page <= totalPages);
+  } catch (error) {
+    console.warn('generateStaticParams: API unreachable, falling back to on-demand ISR.', error);
+    return [];
+  }
+
+  console.log(`generateStaticParams: prebuilding ${params.length} school pages.`);
+  return params;
+}
+
 interface SchoolPageProps {
   params: Promise<{ slug: string }>;
 }
@@ -75,8 +110,10 @@ export async function generateMetadata({ params }: SchoolPageProps): Promise<Met
   }
 }
 
-// Force dynamic rendering
-export const dynamic = 'force-dynamic';
+// ISR: regenerate at most once a week per slug. School data updates annually,
+// so a 7-day cache is plenty and gives sub-100ms TTFB on cache hits.
+export const revalidate = 604800;
+export const dynamicParams = true;
 
 export default async function SchoolPage({ params }: SchoolPageProps) {
   const { slug } = await params;