chore: access model_fields from class instead of instance

[vdusek]

Summary

• Access model_fields from the class (type(configuration).model_fields) instead of the instance (configuration.model_fields) in Configuration.from_configuration

Since Pydantic V2.11, accessing model_fields on an instance emits a PydanticDeprecatedSince211 deprecation warning (to be removed in V3.0).

Test plan

• CI passes

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.54%. Comparing base (c0a74b9) to head (3f554f6).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #800      +/-   ##
==========================================
+ Coverage   85.50%   85.54%   +0.03%     
==========================================
  Files          46       46              
  Lines        2691     2691              
==========================================
+ Hits         2301     2302       +1     
+ Misses        390      389       -1     

Flag	Coverage Δ
e2e	35.48% <0.00%> (ø)
integration	57.63% <0.00%> (+0.03%)	⬆️
unit	72.46% <100.00%> (ø)

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