Toolbar: Toolbar Button

`toolbar_input_button` will be a bootstrap button with sensible default formatting suited for inclusion in a toolbar. It will be designed with an eye towards icon-only buttons, but work for icon + text and text-only as well.

Example:

<img width="251" height="62" alt="Image" src="https://github.com/user-attachments/assets/c705df93-a257-4f1c-9339-566275cb028b" />
