Fix timeline media size

[thai-d-v]

• use Layout to eliminate SceneDelegate and other dependencies
• roll back to grid layout for posts with multiple media items because it is more intuitive
• use a safe number 450 for maximum height because can not detect the height of the scroll view, but it works very well for the layout

[Dimillian]

This is awesome but I really want to keep the carousel for the previews. This is better IMO and also future-proof as some instances support more than 4 media (like Threads soon)

[thai-d-v]

Of course, the carousel is back, I just changed the corner radius to make it consistent.