Fix demo compatibility after Storybook update

[muukii]

Updating Storybook and the supporting UI dependencies left the demo uncompilable, and iOS 27 rejected its legacy app startup. This migrates the demo to the current Book/BookPage catalog and creates its window through SceneDelegate.

All 24 existing demo controller factories remain. UIKit pages embed their controllers directly, while modal demos retain real UIKit presentation. Removed grid, portal, and SwiftUI hosting helpers are replaced with demo-owned adapters. Internal animation diagnostics are limited to Debug so Release builds succeed, and the Detail title now follows light/dark appearance.

The native catalog uses sorted disclosure groups, moves the introduction to an About page, and gives modal demos a page with a launch button.

Validation

• Debug simulator build passed.
• Release build for a generic iOS device passed with signing disabled.
• iOS 27: catalog, search, history, Stage, SwiftUI hosting, ContextMenu, PortalStack, Transition, and Rideau interactions checked.
• iOS 18.6: startup and SafeArea navigation checked.
• git diff --check and plist/project syntax checks passed.

Runtime coverage is representative rather than every interaction in all 24 demos. Signed installation and physical-device execution were not checked. Existing compiler warnings remain.