Add Compare button to map view school list

- Add orange Compare button alongside Details button
- Toggle to Remove when school is in comparison
- Stack buttons vertically with consistent sizing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/styles.css

@@ -570,10 +570,33 @@ body {
     color: var(--text-primary);
 }
 
-.school-list-item-details {
+.school-list-item-actions {
+    display: flex;
+    flex-direction: column;
+    gap: 0.375rem;
     flex-shrink: 0;
-    padding: 0.5rem 0.875rem;
-    font-size: 0.8rem;
+}
+
+.school-list-item-actions .btn {
+    padding: 0.4rem 0.75rem;
+    font-size: 0.75rem;
+    white-space: nowrap;
+}
+
+.btn-compare {
+    background: var(--accent-coral);
+    color: white;
+    border: 1px solid var(--accent-coral);
+}
+
+.btn-compare:hover {
+    background: #d4654a;
+    border-color: #d4654a;
+}
+
+.btn-compare.active {
+    background: var(--text-muted);
+    border-color: var(--text-muted);
 }
 
 /* Search location marker on map */