fix(geoportal): use absolute positioning to fill main (fixes h-full/flex-1 chain)

height: 100% doesn't work when the parent gets its height from flex-1
(flexbox-computed, not explicit height). Fixed by adding position:relative
to main in fullscreen mode and using absolute inset-0 on the geoportal
container.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/modules/geoportal/components/geoportal-module.tsx

@@ -93,7 +93,7 @@ export function GeoportalModule() {
   }, []);
 
   return (
-    <div className="relative h-full w-full">
+    <div className="absolute inset-0">
       {/* Full-bleed map */}
       <MapViewer
         ref={mapHandleRef}

src/shared/components/layout/app-shell.tsx

@@ -61,7 +61,7 @@ export function AppShell({ children }: AppShellProps) {
         <main
           className={cn(
             'flex-1 overflow-y-auto',
-            isFullscreen ? 'overflow-hidden p-0' : 'p-6',
+            isFullscreen ? 'relative overflow-hidden p-0' : 'p-6',
           )}
         >
           {children}