fix(map): results map fullscreen falls back to an overlay on iOS

The results-view map's fullscreen button called requestFullscreen(),
which iOS Safari doesn't implement (fullscreen is video-only there), so
tapping it did nothing on iPhones — the same gap already fixed for the
school hero map.

When the Fullscreen API is missing or its promise rejects, fall back to
a fixed-position overlay (.fsFallback, z-index 5000) driven by state,
locking body scroll while open. Leaflet re-measures on window resize, so
dispatch a resize when fullscreen toggles (the CSS overlay fires none) or
the map would fill only part of the screen. Native fullscreen is
unchanged.

New e2e journey deletes Element.requestFullscreen on a mobile viewport,
opens the results map fullscreen, and asserts the exit control appears
then releases; it fails against current production, reproducing the bug.

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

nextjs-app/components/SchoolMap.module.css

@@ -10,6 +10,15 @@
   height: 100dvh;
 }
 
+/* Fallback fullscreen (iOS Safari — no Element.requestFullscreen): the API
+   can't promote the element, so pin it over the page ourselves. Above the
+   comparison toast (3000) and the bottom nav; below modals (9999+). */
+.mapWrapper.fsFallback {
+  position: fixed;
+  inset: 0;
+  z-index: 5000;
+}
+
 .fullscreenBtn {
   position: absolute;
   top: 0.625rem;