feat: Refactor navigation and UI components

This commit refactors the navigation structure and UI components for better organization and scalability.

Key changes:
- Deleted `HomeViewModel.kt` as it was unused.
- Moved `ContentScreen.kt` to `ui/screens` directory.
- Updated `AppNavigation.kt`:
    - Removed old route definitions and direct component navigation.
    - Integrated new nested navigation graphs for `ButtonGroup` and `ProgressIndicator` examples.
    - Simplified navigation logic in `HomeScreen` to use direct lambda invocations for navigation.
- Created `AppRoutes.kt` to define sealed interfaces for navigation routes, improving type safety and organization.
- Introduced `ListTile.kt` composable for generic list item display.
- Updated `HomeScreen.kt`:
    - Replaced `HomeItem` with `HomeItemData` which now includes an `onClickAction` lambda.
    - Uses `GridTile` for displaying items in the lazy grid.
    - Navigation to examples is now handled by passing lambdas directly (e.g., `onNavigateToButtonGroup`).
- Renamed `HomeItem.kt` to `HomeItemData.kt` and updated its structure to hold an `onClickAction` instead of a `Route`.
- Added `GridTile.kt` composable for displaying items in a grid layout.
- Removed unused `@ExperimentalMaterial3ExpressiveApi` annotation from `MainActivity.kt`.