ci: automate releases with release-please

[rustatian]

• Add Release Please on main. It continues from the v1.6.0 release.
• Use the CI GitHub App token, so the release PRs start the existing checks.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.16%. Comparing base (517df04) to head (c45c1ca).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #31   +/-   ##
=======================================
  Coverage   40.16%   40.16%           
=======================================
  Files           4        4           
  Lines         244      244           
=======================================
  Hits           98       98           
  Misses        146      146           

Flag	Coverage Δ
unittests	40.16% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 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.