fix(a11y): WCAG AA colour contrast across every route (P0.1)

Live axe-core inventory found 13 failing fg/bg pairs (3.12:1 coral text/
fills, 4.0-4.5 teal near-misses, 2.7 gold badge, 1.9 chart-colour text).
All replacement values validated ≥4.5:1 against every background they
sit on:

- --accent-coral-dark deepened to #b04a2e and used for coral text roles
  (nav active, back/map links, kickers, chips) and coral fills under
  white text (btn-primary, phase tabs, section-nav compare, chart chips);
  new --accent-coral-darker #9c3f26 for their hovers. Decorative coral
  (pins, bars, borders, focus ring) keeps the brand #e07256.
- --accent-teal darkened to #296f6f (rankings values, metric rows,
  ofsted grades, eyebrows all pass).
- Ofsted green #3c8c3c→#2f7a2f; off-token gold #b8920e→--accent-gold-text.
- Gender-split pink text #b45778→#a04a68; admissions tip numerals to a
  3.8:1 muted brown (28px display text).
- New CHART_TEXT_COLORS: AA-dark counterparts of the Chart.js series
  palette for compare-card values (swatch dots keep true series colour).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nextjs-app/components/SchoolDetailView.module.css

@@ -13,7 +13,7 @@
     padding: 0.25rem 0;
     font-size: 1.0625rem;
     font-weight: 600;
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
     background: none;
     border: none;
     cursor: pointer;
@@ -76,7 +76,7 @@
 
 .headerHasMap .actions .btnAdd {
     background: rgba(255, 255, 255, 0.9);
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
     border-color: transparent;
     -webkit-backdrop-filter: blur(6px);
     backdrop-filter: blur(6px);
@@ -124,7 +124,7 @@
     padding: 0;
     font: inherit;
     font-weight: 600;
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
     cursor: pointer;
     white-space: nowrap;
 }
@@ -210,7 +210,7 @@
 }
 
 .genderSplitGirls {
-    color: #b45778;
+    color: #a04a68;
 }
 
 .genderSplitBoys {
@@ -242,7 +242,7 @@
 }
 
 .genderBarGirls {
-    background: #b45778;
+    background: #a04a68;
 }
 
 .genderBarBoys {
@@ -270,12 +270,12 @@
 }
 
 .btnAdd {
-    background: var(--accent-coral, #e07256);
+    background: var(--accent-coral-dark, #b04a2e);
     color: white;
 }
 
 .btnAdd:hover {
-    background: var(--accent-coral-dark, #c45a3f);
+    background: var(--accent-coral-darker, #9c3f26);
     transform: translateY(-1px);
 }
 
@@ -323,7 +323,7 @@
     padding: 0.3rem 0.625rem;
     font-size: 0.75rem;
     font-weight: 600;
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
     background: none;
     border: 1px solid var(--border-color, #e5dfd5);
     border-radius: 4px;
@@ -399,7 +399,7 @@
 }
 
 .sectionNavLinkActive {
-    background: var(--accent-coral, #e07256);
+    background: var(--accent-coral-dark, #b04a2e);
     color: white;
     font-weight: 600;
 }
@@ -468,8 +468,8 @@
     width: 38px;
     height: 38px;
     border-radius: 9px;
-    border: 1px solid var(--accent-coral, #e07256);
-    background: var(--accent-coral, #e07256);
+    border: 1px solid var(--accent-coral-dark, #b04a2e);
+    background: var(--accent-coral-dark, #b04a2e);
     color: white;
     cursor: pointer;
     transition: background 0.15s ease, border-color 0.15s ease;
@@ -513,8 +513,8 @@
     font-size: 0.75rem;
     font-weight: 600;
     color: white;
-    background: var(--accent-coral, #e07256);
-    border: 1px solid var(--accent-coral, #e07256);
+    background: var(--accent-coral-dark, #b04a2e);
+    border: 1px solid var(--accent-coral-dark, #b04a2e);
     border-radius: 999px;
     cursor: pointer;
     white-space: nowrap;
@@ -522,8 +522,8 @@
 }
 
 .sectionNavCompare:hover {
-    background: var(--accent-coral-dark, #c45a3f);
-    border-color: var(--accent-coral-dark, #c45a3f);
+    background: var(--accent-coral-darker, #9c3f26);
+    border-color: var(--accent-coral-darker, #9c3f26);
 }
 
 .sectionNavCompareIn {
@@ -626,7 +626,7 @@
 }
 
 .sectionsTick {
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
 }
 
 /* On phones the menu becomes a bottom sheet. */
@@ -856,7 +856,7 @@
 }
 
 .progressNegative {
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
     font-weight: 700;
 }
 
@@ -868,12 +868,12 @@
 
 .statusWarn {
     background: var(--accent-gold-bg);
-    color: #b8920e;
+    color: var(--accent-gold-text, #7a6800);
 }
 
 .statusBad {
     background: var(--accent-coral-bg);
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
 }
 
 /* Charts Section */
@@ -1011,15 +1011,15 @@
 }
 .ofstedGrade2 {
     background: rgba(60, 140, 60, 0.12);
-    color: #3c8c3c;
+    color: #2f7a2f;
 }
 .ofstedGrade3 {
     background: var(--accent-gold-bg);
-    color: #b8920e;
+    color: var(--accent-gold-text, #7a6800);
 }
 .ofstedGrade4 {
     background: var(--accent-coral-bg);
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
 }
 
 /* Report Card grade colours (5-level scale, lower = better) */
@@ -1029,11 +1029,11 @@
 } /* Exceptional */
 .rcGrade2 {
     background: rgba(60, 140, 60, 0.12);
-    color: #3c8c3c;
+    color: #2f7a2f;
 } /* Strong */
 .rcGrade3 {
     background: var(--accent-gold-bg);
-    color: #b8920e;
+    color: var(--accent-gold-text, #7a6800);
 } /* Expected standard */
 .rcGrade4 {
     background: rgba(249, 115, 22, 0.12);
@@ -1041,7 +1041,7 @@
 } /* Needs attention */
 .rcGrade5 {
     background: var(--accent-coral-bg);
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
 } /* Urgent improvement */
 
 /* Safeguarding value (used inside a standard metricCard) */
@@ -1061,7 +1061,7 @@
     font-size: 0.8125rem;
     font-weight: 700;
     background: var(--accent-coral-bg);
-    color: var(--accent-coral, #e07256);
+    color: var(--accent-coral-dark, #b04a2e);
 }
 
 .ofstedDisclaimer {