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/components/EditorialSection.tsx

@@ -0,0 +1,59 @@
+// Server component: pure markup, no client state.
+
+import styles from './HomeView.module.css';
+
+interface EditorialSectionProps {
+  totalSchools: number | null;
+  localAuthorityCount: number;
+}
+
+export function EditorialSection({ totalSchools, localAuthorityCount }: EditorialSectionProps) {
+  return (
+    <section className={styles.editorial}>
+      <div className={styles.editorialGrid}>
+        <div className={styles.editorialText}>
+          <div className={styles.editorialKicker}>About school data</div>
+          <h2 className={styles.editorialHeading}>Making UK school performance data actually readable</h2>
+          <p>
+            School performance data in England is rich but fragmented. The Department for Education publishes
+            Key Stage 2 SATs, GCSE attainment, Ofsted outcomes, progress scores, admissions figures and
+            demographics — each in its own table, each with its own jargon.
+          </p>
+          <p>
+            SchoolCompare brings it all into one place. Every school page shows performance against the national
+            average, explains what the numbers mean, and lets you shortlist schools side by side. Built for
+            parents, governors, journalists, and anyone who wants to understand a school without reading a
+            40-page inspection report.
+          </p>
+        </div>
+        <div className={styles.factbox}>
+          <h3 className={styles.factboxHeading}>Coverage at a glance</h3>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Schools covered</span>
+            <span className={styles.factVal}>{totalSchools ? `${totalSchools.toLocaleString()}` : '24,000+'}</span>
+          </div>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Local authorities</span>
+            <span className={styles.factVal}>{localAuthorityCount > 0 ? localAuthorityCount : 152}</span>
+          </div>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Phases</span>
+            <span className={styles.factVal}>Primary &amp; Secondary</span>
+          </div>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Latest results year</span>
+            <span className={styles.factVal}>2024/25</span>
+          </div>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Historical data</span>
+            <span className={styles.factVal}>2016–2025</span>
+          </div>
+          <div className={styles.factRow}>
+            <span className={styles.factKey}>Metrics per school</span>
+            <span className={styles.factVal}>40+</span>
+          </div>
+        </div>
+      </div>
+    </section>
+  );
+}