Move /platform/detection vars into /env (#9707)

* Add platform vars to env

* Replace /platform/detection with /env

src/screens/PostThread/components/GrowthHack.tsx

@@ -3,10 +3,10 @@ import {View} from 'react-native'
 import {PrivacySensitive} from 'expo-privacy-sensitive'
 
 import {useAppState} from '#/lib/hooks/useAppState'
-import {isIOS} from '#/platform/detection'
 import {atoms as a, useTheme} from '#/alf'
 import {sizes as iconSizes} from '#/components/icons/common'
 import {Mark as Logo} from '#/components/icons/Logo'
+import {IS_IOS} from '#/env'
 
 const ICON_SIZE = 'xl' as const
 
@@ -25,7 +25,7 @@ export function GrowthHack({
 
   const appState = useAppState()
 
-  if (!isIOS || appState !== 'active') return children
+  if (!IS_IOS || appState !== 'active') return children
 
   return (
     <View