Fix map view layout and z-index issues

- Move location-info banner above map view as full-width bar
- Set fixed height for map view container with equal map/list heights
- Add z-index to map to prevent overlap with sticky header
- Update mobile responsive styles for consistent heights

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

frontend/app.js

@@ -601,8 +601,8 @@ function updateLocationInfoBanner(searchLocation) {
         <span>Showing schools within ${searchLocation.radius} miles of <strong>${searchLocation.postcode.toUpperCase()}</strong></span>
     `;
 
-  // Insert banner before the schools grid
-  elements.schoolsGrid.parentNode.insertBefore(banner, elements.schoolsGrid);
+  // Insert banner before the results container (above map view)
+  elements.resultsContainer.parentNode.insertBefore(banner, elements.resultsContainer);
 }
 
 async function searchByLocation() {