feat(detail): replace SATs text tables with cascade bar charts, add admissions bar and history accordion

Redesign the School Details page for better parent comprehension:
- New SatsChart component: horizontal cascade bars with ruler scale and
  national average marker (teal/coral palette matching site theme)
- Admissions section: visual progress bar showing 1st-preference demand
  vs available places, colour-coded by oversubscription status
- Historical data: collapse raw year-by-year table behind a disclosure
  element while keeping the performance line chart always visible
- EAL metric: add national average comparison via DeltaChip (backend now
  includes eal_pct in national averages endpoint)
- New formatWithSuppression utility for null/suppressed data handling

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextjs-app/components/SchoolDetailView.module.css

@@ -894,3 +894,105 @@
     margin-top: 1rem;
   }
 }
+
+/* ── Progress scores row (below SatsChart) ── */
+.progressScoresRow {
+  margin-top: 1.25rem;
+  padding-top: 1rem;
+  border-top: 1px solid var(--border-color, #e5dfd5);
+}
+
+.progressScoresGrid {
+  display: flex;
+  gap: 1.5rem;
+  flex-wrap: wrap;
+}
+
+.progressScoreItem {
+  display: flex;
+  align-items: baseline;
+  gap: 0.4rem;
+}
+
+.progressScoreLabel {
+  font-size: 0.78rem;
+  font-weight: 500;
+  color: var(--text-muted, #6d685f);
+}
+
+.progressScoreValue {
+  font-size: 0.9rem;
+  font-weight: 700;
+  color: var(--text-primary, #1a1612);
+  font-variant-numeric: tabular-nums;
+}
+
+/* ── Admissions progress bar ── */
+.admissionsBarWrap {
+  margin-bottom: 1rem;
+}
+
+.admissionsBarLabel {
+  font-size: 0.8125rem;
+  color: var(--text-secondary, #5c564d);
+  margin-bottom: 0.4rem;
+}
+
+.admissionsBarLabel strong {
+  color: var(--text-primary, #1a1612);
+  font-weight: 700;
+}
+
+.admissionsBarTrack {
+  height: 20px;
+  background: var(--bg-secondary, #f3ede4);
+  border-radius: 10px;
+  overflow: hidden;
+  position: relative;
+}
+
+.admissionsBarFill {
+  height: 100%;
+  border-radius: 10px;
+  transition: width 0.6s ease;
+}
+
+.admissionsBarOversubscribed {
+  background: var(--accent-coral, #e07256);
+}
+
+.admissionsBarUndersubscribed {
+  background: var(--accent-teal, #2d7d7d);
+}
+
+/* ── History accordion ── */
+.historyDisclosure {
+  margin-top: 1rem;
+}
+
+.historyToggle {
+  font-size: 0.8125rem;
+  font-weight: 600;
+  color: var(--text-muted, #6d685f);
+  cursor: pointer;
+  padding: 0.5rem 0;
+  list-style: none;
+  display: flex;
+  align-items: center;
+  gap: 0.4rem;
+}
+
+.historyToggle::-webkit-details-marker {
+  display: none;
+}
+
+.historyToggle::before {
+  content: '▸';
+  display: inline-block;
+  transition: transform 0.2s ease;
+  font-size: 0.7rem;
+}
+
+.historyDisclosure[open] > .historyToggle::before {
+  transform: rotate(90deg);
+}