[Demian-Yushyn]

On iPhone Duo the window changes size as the device opens, folds and rotates, and the system moves
the status bar and tab bar into a column at the side. The app picked its layout from the device
orientation and idiom, so on Duo the tab content collapsed to zero height, cards slid under the side
column and custom headers touched the top edge. Layout now follows the window's size classes and
safe areas, as Designing for iPhone Duo asks.

Changes

• Size classes instead of device checks. New Core/Core/Extensions/LayoutEnvironment.swift:
  isHorizontalLayout (compact height) replaces isHorizontal in 43 files, layoutIdiom
  (regular × regular → .pad) replaces layout checks of userInterfaceIdiom in 16. iPhone and iPad
  get the same values as before; the Duo inner display gets the iPad layouts.

• Tab bar is styled through UITabBarAppearance. The legacy isTranslucent/backgroundColor
  broke the vertical tab bar.

• Safe areas. 15 screens no longer ignore the horizontal safe area. minimumTopSafeArea() keeps
  custom headers off the top edge when the status bar is on the side.

• Screens without a tab bar are centred. AppNavigationController keeps the side column only on
  the main tabs and in compact height. It uses iOS 27.1 API, compiled only with an SDK that has it.

• Scene life cycle (SceneDelegate), which iPhone Duo requires for resizable apps.

• Course back button stays on screen when the course header collapses (scrolling down, or the
  device in landscape) and moves onto the collapsed title row, so it no longer covers the course tabs.

• Smaller fixes: the YouTube player keeps playing through rotation and folding, Course details
  picks one or two columns from the window shape.

  Screenshots

Before → after (outer display)

	Before	After
Discover
Profile: content empty
Settings: cards under the status bar
Sign in: off centre
Unit: back button at the top edge

All screens: outer and inner display, portrait and landscape

Screen	Outer, portrait	Outer, landscape	Inner, portrait	Inner, landscape
Sign in
Dashboard
Discover
Profile
Edit profile
Settings
Course content
Course home
Course section
Unit: text
Unit: video

[openedx-webhooks]

Thanks for the pull request, @Demian-Yushyn!

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[RawanMatar89]

LGTM