fix: iOS 27 example apps compatibility (#1499)

## 📜 Description

Fixed app crash at app launch on iOS 27 for iOS example projects.

## 💡 Motivation and Context

The iOS example apps crashed on launch when built with the latest iOS
SDK because UIKit now requires apps to adopt the `UIScene` lifecycle.
The examples still created their main `UIWindow` directly from
`AppDelegate` and did not declare a scene manifest.

This change migrates the example apps to scene-based lifecycle startup
so they can launch correctly with the current SDK.

## 📢 Changelog

### iOS

- added `SceneDelegate` support for the example and Fabric example apps.
- added `UIApplicationSceneManifest` entries and moved React Native
window startup into the scene lifecycle.

## 🤔 How Has This Been Tested?

Tested in example app (fabric/paper) on iOS 27.0 public beta (iPhone 17
Pro, simulator).

## 📸 Screenshots (if appropriate):

|Before|After|
|-------|-----|
|<img width="1689" height="1026" alt="Screenshot 2026-06-15 at 16 44 47"
src="https://github.com/user-attachments/assets/f5fc8c4d-d72d-47bf-b018-7288974315b4"
/>|<img width="340" height="751" alt="image"
src="https://github.com/user-attachments/assets/c9318d0b-e8a6-47e9-a532-5bde6040c815"
/>|

## 📝 Checklist

- [x] CI successfully passed
- [x] I added new mocks and corresponding unit-tests if library API was
changed