refactor: Deprecate showFab on BrandHeroScreen

lib/ui/layouts/brand_hero_screen.dart

@@ -9,7 +9,7 @@ class BrandHeroScreen extends StatelessWidget {
     required this.children,
     super.key,
     this.hasBackButton = true,
-    this.hasFlashButton = true,
+    this.hasFlashButton = false,
     this.heroIcon,
     this.heroIconWidget,
     this.heroTitle = '',
@@ -20,6 +20,7 @@ class BrandHeroScreen extends StatelessWidget {
 
   final List<Widget> children;
   final bool hasBackButton;
+  @Deprecated('Flash button is now provided by root scaffold')
   final bool hasFlashButton;
   final IconData? heroIcon;
   final Widget? heroIconWidget;

lib/ui/layouts/root_scaffold_with_navigation.dart

@@ -52,6 +52,9 @@ class RootScaffoldWithNavigation extends StatelessWidget {
         hidden: !(Breakpoints.small.isActive(context) && showBottomBar),
         key: const Key('bottomBar'),
       ),
+      floatingActionButton: showFab && Breakpoints.small.isActive(context)
+          ? const BrandFab()
+          : null,
     );
   }
 }