ci: add workflow to regenerate models from OpenAPI spec

[vdusek]

Summary

• Add workflow_dispatch workflow that regenerates Pydantic models from an apify-docs PR's OpenAPI spec
• Builds the spec locally, runs datamodel-codegen, and opens a PR if models changed
• Comments back on the source apify-docs PR with a link

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.93%. Comparing base (b778c20) to head (3097e61).
⚠️ Report is 25 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #694      +/-   ##
==========================================
+ Coverage   94.80%   94.93%   +0.13%     
==========================================
  Files          45       45              
  Lines        4404     4403       -1     
==========================================
+ Hits         4175     4180       +5     
+ Misses        229      223       -6     

Flag	Coverage Δ
integration	94.93% <ø> (+0.13%)	⬆️

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