chore: Add Python 3.14 tests

[effigies]

This also adds a uv.lock to replace our various requirements.txt files.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.43%. Comparing base (b5ecf48) to head (f05e505).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1431      +/-   ##
==========================================
+ Coverage   95.34%   95.43%   +0.09%     
==========================================
  Files         209      209              
  Lines       29780    29784       +4     
  Branches     3357     4472    +1115     
==========================================
+ Hits        28393    28425      +32     
+ Misses        948      926      -22     
+ Partials      439      433       -6     

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