Replace Custom Preview Annotations with Official Tooling @PreviewLightDark and @PreviewScreenSizes

[hmzgtl16]

What I have done and why

I have replaced the custom preview annotations used in the nowinandroid repository with the official, standardized alternatives from the $\text{androidx.compose.ui.tooling.preview}$ library.

This work was executed in two main steps:

1. Replaced $\text{ThemePreviews}$ with $\text{@PreviewLightDark}$: The custom annotation for showing a Composable in light and dark mode was replaced by the official $\text{@PreviewLightDark}$. This allowed for the removal of the custom $\text{ThemePreviews}$ definition file, simplifying the code.
2. Replaced $\text{DevicePreviews}$ with $\text{@PreviewScreenSizes}$: The custom annotation for displaying a Composable across different screen sizes was replaced by the official $\text{@PreviewScreenSizes}$. This standardized the way we check for responsive UI behavior and allowed for the removal of the outdated $\text{DevicePreviews}$ definition file.

All corresponding custom utility files were removed following these replacements, resulting in a cleaner and more maintainable preview setup.

Related issues/PRs:

1923