Fix "Want to read" button clipped on mobile

[RayBB]

It has been bothering me for a while that the want to read button looks funny in the corners of the button.

It looks like this:

After my PR it looks like this:

PS: I set the width of the dropdown button to match the width of the listen button. But I'm not attached to that change.

screenshot of listen button.

Technical

Had to move the border radius code one level down to be able to hide overflow.

Did a few more small css cleanups while I was in there.

I explain more in the demo video below.

Testing

To see this change locally on search results you might need to enable my_books_dropper in openlibrary.yml

Screenshot

Demo and code walkthrough: https://www.loom.com/share/b571d2aefbf4443890f9a9a345f14646

Stakeholders

Related to #8181 so I'll tag @jimchamp

[codecov-commenter]

Codecov Report

Merging #8414 (670f535) into master (337b7b0) will not change coverage.
Report is 1 commits behind head on master.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #8414   +/-   ##
=======================================
  Coverage   16.62%   16.62%           
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  Files          84       84           
  Lines        4433     4433           
  Branches      758      758           
=======================================
  Hits          737      737           
  Misses       3212     3212           
  Partials      484      484           

[mekarpeles]

Thank you!