Keyboard Shortcuts

I think it's a good idea to implement keyboard shortcuts to enhance the UI.

For example:
- Use Enter to submit an answer.
- Press CTRL + Space to replay audio.
- Etc

Start by locating the UI entry points for submitting an answer and replaying audio, then check how keyboard events are currently handled. Define the supported shortcuts, including Enter and Ctrl+Space, and verify that each triggers the corresponding action without disrupting normal input.

Written by the indexing model from the issue text.