feat(ux): implement comprehensive UX audit fixes across all pages

Addresses 28 issues identified in UX audit (P0–P3 severity):

P0 — Critical:
- Fix compare URL sharing: seed ComparisonContext from SSR initialData
  when localStorage is empty, making /compare?urns=... links shareable
- Remove permanently broken "Avg. Scaled Score" column from school
  detail historical data table

P1 — High priority:
- Add radius selector (0.5–10 mi) to postcode search in FilterBar
- Make Add to Compare a toggle (remove) on SchoolCards
- Hide hero title/description once a search is active
- Show school count + quick-search prompts on empty landing page
- Compare empty state opens in-page school search modal directly
- Remove URN from school detail header (irrelevant to end users)
- Move map above performance chart in school detail page
- Add ← Back navigation to school detail page
- Add sort controls to search results (RWM%, distance, A–Z)
- Show metric descriptions below metric selector
- Expand ComparisonToast to list school names with per-school remove
- Add progress score explainer (0 = national average) throughout

P2 — Medium:
- Remove console.log statements from ComparisonView
- Colour-code comparison school cards to match chart line colours
- Replace plain loading text with LoadingSkeleton in ComparisonView
- Rankings empty state uses shared EmptyState component
- Rankings year filter shows actual year e.g. "2023 (Latest)"
- Rankings subtitle shows top-N count
- Add View link alongside Add button in rankings table
- Remove placeholder Privacy Policy / Terms links from footer
- Replace untappable 10px info icons with visible metric hint text
- Show active filter chips in search results header

P3 — Polish:
- Remove redundant "Home" nav link (logo already links home)
- Add / and Ctrl+K keyboard shortcut to focus search input
- Add Share button to compare page (copies URL to clipboard)

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

nextjs-app/components/ComparisonToast.module.css

@@ -20,14 +20,15 @@
 
 .toastContent {
   display: flex;
-  align-items: center;
-  gap: 1.5rem;
-  padding: 0.75rem 1rem 0.75rem 1.25rem;
+  flex-direction: column;
+  gap: 0;
+  padding: 1rem 1.25rem;
   background: var(--bg-accent, #1a1612);
   color: var(--text-inverse, #faf7f2);
-  border-radius: 50px;
+  border-radius: 16px;
   box-shadow: 0 10px 30px rgba(26, 22, 18, 0.3);
   border: 1px solid rgba(255, 255, 255, 0.1);
+  min-width: 260px;
 }
 
 .toastInfo {
@@ -59,6 +60,8 @@
   display: flex;
   align-items: center;
   gap: 0.75rem;
+  padding-top: 0.25rem;
+  border-top: 1px solid rgba(255, 255, 255, 0.1);
 }
 
 .btnClear {
@@ -93,6 +96,65 @@
   background: var(--bg-secondary, #f3ede4);
 }
 
+.toastHeader {
+  display: flex;
+  align-items: center;
+  margin-bottom: 0.5rem;
+}
+
+.toastTitle {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  font-weight: 600;
+  font-size: 0.875rem;
+  color: var(--text-inverse, #faf7f2);
+}
+
+.schoolList {
+  display: flex;
+  flex-direction: column;
+  gap: 0.25rem;
+  margin-bottom: 0.75rem;
+  max-height: 120px;
+  overflow-y: auto;
+}
+
+.schoolItem {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.5rem;
+  padding: 0.25rem 0.375rem;
+  background: rgba(255, 255, 255, 0.08);
+  border-radius: var(--radius-sm, 4px);
+}
+
+.schoolName {
+  font-size: 0.8rem;
+  color: var(--text-inverse, #faf7f2);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+}
+
+.removeSchoolBtn {
+  background: none;
+  border: none;
+  color: rgba(250, 247, 242, 0.5);
+  cursor: pointer;
+  font-size: 1rem;
+  padding: 0 0.25rem;
+  line-height: 1;
+  flex-shrink: 0;
+  transition: color 0.2s ease;
+}
+
+.removeSchoolBtn:hover {
+  color: var(--text-inverse, #faf7f2);
+}
+
 @media (max-width: 640px) {
   .toastContainer {
     bottom: 1.5rem;
@@ -100,8 +162,7 @@
   }
 
   .toastContent {
-    flex-direction: column;
-    gap: 1rem;
+    gap: 0;
     border-radius: 16px;
     padding: 1.25rem;
   }