chore(mobile): add box shadow to asset details (#27510)

The details widget can blend with the image when they are similar
colours.

mobile/lib/presentation/widgets/asset_viewer/asset_details.widget.dart

@@ -26,6 +26,14 @@ class AssetDetails extends ConsumerWidget {
       decoration: BoxDecoration(
         color: context.colorScheme.surface,
         borderRadius: const BorderRadius.vertical(top: Radius.circular(20)),
+        boxShadow: [
+          BoxShadow(
+            color: Colors.black.withValues(alpha: 0.2),
+            offset: const Offset(0, -3),
+            blurRadius: 10,
+            spreadRadius: 2,
+          ),
+        ],
       ),
       child: SafeArea(
         top: false,