ci: use codecov token

[cakebaker]

This PR uses the codecov token which is required with codecov-action@v4.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.30%. Comparing base (57d801c) to head (e2d7ed6).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
+ Coverage   49.00%   51.30%   +2.29%     
==========================================
  Files          18       18              
  Lines        2216     2306      +90     
  Branches      309      333      +24     
==========================================
+ Hits         1086     1183      +97     
+ Misses       1082     1060      -22     
- Partials       48       63      +15     

Flag	Coverage Δ
macos_latest	50.71% <ø> (+2.33%)	⬆️
ubuntu_latest	46.57% <ø> (+2.60%)	⬆️
windows_latest	0.10% <ø> (-0.01%)	⬇️

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