fix: correct broken LICENSE link in README

[farhan]

Summary

The README's License section linked to [LICENSE](LICENSE), but the license file in this repo is named LICENSE.txt — so the link 404s on GitHub and in the rendered docs. This points it at the actual filename.

-This project is licensed under the AGPL-3.0 License - see the [LICENSE](LICENSE) file for details.
+This project is licensed under the AGPL-3.0 License - see the [LICENSE](LICENSE.txt) file for details.

Why fix:

Beyond correcting the broken link, this is a fix: commit so python-semantic-release cuts the next patch release (1.7.6 → 1.7.7), exercising the release pipeline end-to-end now that the immutable-safe release workflow (#77) is in place.

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🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.17%. Comparing base (fb81a86) to head (f69a7ae).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #78   +/-   ##
=======================================
  Coverage   82.17%   82.17%           
=======================================
  Files          48       48           
  Lines        1419     1419           
  Branches      110      110           
=======================================
  Hits         1166     1166           
  Misses        221      221           
  Partials       32       32           

Flag	Coverage Δ
unittests	82.17% <ø> (ø)

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