Update versions of everything

[teutoburg]

• Python version for non-matrix workflows now always 3.13
• Poetry version now always 2.3.0 (latest)
• Artifact upload and download actions updated according to dependabot
• pytest and pytest-cov updated to match ecosystem-wide versions

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b473691) to head (856fea6).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #79   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines            7         7           
=========================================
  Hits             7         7           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.