feat: Add Android TV D-pad navigation support with tvOptions

[TheNoumanDev]

Summary

• Add D-pad focus navigation system for Android TV using coordinate-based tvOptions in YAML
• Support both host app integration (via TVFocusProvider) and standalone mode for Ensemble(via TVFocusWidget)
• Gate all TV code behind Device().isTV check to prevent impact on mobile/web

Key Changes

Core TV Infrastructure

• device.dart: isTV getter checks Android TV system features (android.hardware.type.television, android.software.leanback)
• tv_focus_provider.dart: Interface for host app focus integration with rowOffset/orderOffset support
• tv_focus_widget.dart: Built-in D-pad navigation with grid-based focus traversal
• tv_focus_order.dart: Coordinate system (row, order, isRowEntryPoint)
• tv_focus_theme.dart: Focus styling resolution (theme > provider > primary color)

Widget Support

• box_wrapper.dart: TV focus wrapping for BoxController-based widgets (~30 widgets)
• form_helper.dart + input_wrapper.dart: TV focus support for FormFieldController widgets (~10 widgets)
• controllers.dart: TVOptionsComposite class with focus styling overrides

Theme Integration

• theme_loader.dart: Parse Tokens.TV.* for focus styling
• theme_manager.dart: Pass tokensOverrides to include TV tokens in EnsembleThemeExtension
• screen_controller.dart: Wrap externally navigated screens with Theme for TV focus colors

Example of style override:

Column:
    styles:
        tvOptions:
            row: 0
            order: 0
            isRowEntryPoint: true
            focusBorderRadius: 8  # Optional per-widget override
    onTap: ...

For testing purpose, release ensemble-v1.2.35-beta.1 version

Screen recording: https://drive.google.com/file/d/1dXP4UByfQRXY5DLpHA2V3pYHR_wPVWdc/view?usp=sharing