Add runtime appearance overrides without restarting the app

[jeremyfrancis55]

Summary

• add System::setAppearance() for light, dark, and system app-local overrides
• add Android and iOS System.SetAppearance bridge functions
• drive Android Material chrome and native node dark variants from shared Compose state
• update system bar styling and System.GetAppearance without recreating MainActivity

Problem

Using Android's normal day/night delegate recreates the activity so Compose picks up the new theme. In a NativePHP app that also restarts the PHP host and can clear the authenticated runtime session, making an in-app light/dark toggle appear to log the user out. Updating only system bars avoids the restart but leaves Compose/native renderers on the old palette.

This change applies the override as snapshot state instead. Compose recomposes in place, the PID and PHP runtime remain alive, and AppearanceChanged still reaches PHP. iOS uses the existing window-level overrideUserInterfaceStyle mechanism.

Testing

• full PHP suite: 928 tests, 3,079 assertions (pass; existing PHP 8.5 deprecation/risky notices remain)
• PHPStan on changed PHP API: pass
• Pint on changed PHP files: pass
• Android Gradle :app:assembleDebug: pass in a NativePHP app using these templates
• emulator dark -> light -> dark: full native UI and system bars update; PID remains unchanged and no activity relaunch occurs

Companion PR

NativePHP/mobile-ui#84 updates every Android plugin renderer to consume the shared state: NativePHP/mobile-ui#84

[jeremyfrancis55]

I realized I can just store the logged in credentials in secure storage..