Fix datetime timezone reference and improve asynchronous handling

[CharlesCNorton]

Summary: This pull request addresses a few minor issues and improvements in the Elia class implementation for the chat application.

Changes:

1. Fixed datetime timezone reference:

   • Corrected datetime.UTC to datetime.timezone.utc to ensure the proper timezone is used for timestamps.

2. Improved asynchronous handling:

   • Added await to push_screen and pop_screen methods to maintain asynchronous behavior and ensure that screens are handled correctly within the app's lifecycle.

3. Code clarity and formatting:

   • Made minor formatting adjustments and improved comments for better readability and maintainability.

Impact:

• These changes ensure accurate timezone handling, improve the app's asynchronous behavior, and enhance code clarity for future maintenance.

Please review the changes and provide feedback. Thank you!

[darrenburns]

thanks!