Move the back-button in front of banner (#5748)

src/screens/Profile/Header/GrowableBanner.tsx

···
   if (!pagerContext || !isIOS) {
     return (
       <View style={[a.w_full, a.h_full]}>
-        {backButton}
         {children}
+        {backButton}
       </View>
     )
   }

src/screens/Profile/Header/Shell.tsx

···
   return (
     <View style={t.atoms.bg} pointerEvents={isIOS ? 'auto' : 'box-none'}>
       <View
-        pointerEvents={isIOS ? 'auto' : 'none'}
+        pointerEvents={isIOS ? 'auto' : 'box-none'}
         style={[a.relative, {height: 150}]}>
         <GrowableBanner
           backButton={