Buttons enhancement inside the Donut platform

## **Problem to be solved**

Buttons within the platform do not hold consistency. So the purpose of this issue is to sort out any inconsistencies related to the buttons we have inside the donut platform.

These are the following things that need to be resolved:
- Convert all the buttons from the round shape to the rectangle shape
- Buttons should have the same font family,, across the whole platform i.e."Inter"
- Remove any shadows
- **Fill color** for the buttons should be the same.