ci: automate releases with release-please

[rustatian]

Reason for This PR

Automate releases from Conventional Commits.

Description of Changes

• Add Release Please on master. It continues from the v6.0.0 release.
• Use the CI GitHub App token, so the release PRs start the existing checks.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

• All commits in this PR are signed (git commit -s -S).
• The reason for this PR is clearly provided.
• The description of changes is clear and encompassing.
• Any required documentation changes are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.

[Copilot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.48%. Comparing base (e4670d9) to head (f6c9a7c).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #293   +/-   ##
=======================================
  Coverage   88.48%   88.48%           
=======================================
  Files          29       29           
  Lines        1346     1346           
=======================================
  Hits         1191     1191           
  Misses        155      155           

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