feat(seo): add school name to URLs, fix sticky nav, collapse compare widget

- URLs now /school/138267-school-name instead of /school/138267
- Bare URN URLs redirect to canonical slug (backward compat)
- Remove overflow-x:hidden that broke sticky tab nav on secondary pages
- ComparisonToast starts collapsed — user must click to open

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

nextjs-app/components/LeafletMapInner.tsx

@@ -9,6 +9,7 @@ import { useEffect, useRef } from 'react';
 import L from 'leaflet';
 import 'leaflet/dist/leaflet.css';
 import type { School } from '@/lib/types';
+import { schoolUrl } from '@/lib/utils';
 
 // Fix for default marker icons in Next.js
 delete (L.Icon.Default.prototype as any)._getIconUrl;
@@ -60,7 +61,7 @@ export default function LeafletMapInner({ schools, center, zoom, onMarkerClick }
             <strong style="font-size: 14px; display: block; margin-bottom: 8px;">${school.school_name}</strong>
             ${school.local_authority ? `<div style="font-size: 12px; color: #666; margin-bottom: 4px;">${school.local_authority}</div>` : ''}
             ${school.school_type ? `<div style="font-size: 12px; color: #666; margin-bottom: 8px;">${school.school_type}</div>` : ''}
-            <a href="/school/${school.urn}" style="display: inline-block; margin-top: 8px; padding: 6px 12px; background: #e07256; color: white; text-decoration: none; border-radius: 4px; font-size: 12px;">View Details</a>
+            <a href="${schoolUrl(school.urn, school.school_name)}" style="display: inline-block; margin-top: 8px; padding: 6px 12px; background: #e07256; color: white; text-decoration: none; border-radius: 4px; font-size: 12px;">View Details</a>
           </div>
         `;