Onboarding fixes (#4508)

* Add extra padding to bottom of profile step

* Make profile pic gen higher res

src/screens/Onboarding/Layout.tsx

@@ -152,7 +152,7 @@ export function Layout({children}: React.PropsWithChildren<{}>) {
               {children}
             </View>
 
-            <View style={{height: 200}} />
+            <View style={{height: 400}} />
           </View>
         </View>
       </ScrollView>

src/screens/Onboarding/StepProfile/PlaceholderCanvas.tsx

@@ -5,7 +5,7 @@ import ViewShot from 'react-native-view-shot'
 import {useAvatar} from '#/screens/Onboarding/StepProfile/index'
 import {atoms as a} from '#/alf'
 
-const SIZE_MULTIPLIER = 1.5
+const SIZE_MULTIPLIER = 5
 
 export interface PlaceholderCanvasRef {
   capture: () => Promise<string>