Migrate Home page animation to CSS transitions and remove react-transition-group

[mstange]

(untested, I found this in my local tree)

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 85.63%. Comparing base (191ff2e) to head (b91bec5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5649   +/-   ##
=======================================
  Coverage   85.63%   85.63%           
=======================================
  Files         312      312           
  Lines       30867    30867           
  Branches     8490     8490           
=======================================
  Hits        26434    26434           
  Misses       4009     4009           
  Partials      424      424           

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