fix(web): quiz button full width at xs and sm viewports

[Kneesal]

Background

The quiz button wrapper currently shrinks to w-auto at the sm breakpoint, making it narrower than expected on small screens. It should remain full-width through sm and only begin shrinking at md.

Expected outcome

The quiz button is 100% width at xs and sm viewports and retains its current sizing at md and above.

Acceptance criteria

• Quiz button wrapper is w-full at xs and sm
• At md the wrapper becomes w-auto
• lg, xl, and 2xl sizing is unchanged

Possible solution(s)

1. Change sm:w-auto to md:w-auto on the wrapper div in QuizButton.tsx.

References

• apps/web/src/components/sections/QuizButton.tsx