Remove Tailwind JS config

[robertknight]

Going forwards downstream projects must use CSS-based config instead, which is the preferred method in Tailwind v4.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4f61d6c) to head (05b75b6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2097   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           71        71           
  Lines         1364      1364           
  Branches       509       509           
=========================================
  Hits          1364      1364           

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[robertknight]

All downstream projects have been converted to use CSS-based config for Tailwind, so we can ship this now.