Material 3 Expressive Theme

### Checks

- [x] I have read the Wiki, searched the open issues, and still think this is a new feature.

### Explain the problem clearly and succinctly:

_No response_

### Describe the solution you'd like:

Hi!
Thanks for this awesome app!
I know you are busy and working in this app in your free time.
If you have time and interest can you add `Material 3 Expressive` theme in this app?

### Describe alternatives you've considered:

_No response_

### Additional context:

_No response_

No file, test, or entry point is identified in the issue. Start by reviewing the existing Android theme implementation and how Material Design themes are organized; define the desired Material 3 Expressive scope and confirm that the new theme is available and visually correct throughout the app.

Written by the indexing model from the issue text.