chore: 🍨 address MG concerns

- take out period (.) from the button name
- prevent clickable buttons till plot is rendered in the custom plot tab
- rename MAIDR in about page
- replace the maidr logo tab name with "About Us"
- use ui.tags.main() to as a main container to surround the main display area such that screen-reader can semantically recognize the main landmark.

Author: SK-143381