Group Dependabot updates

[samdark]

Replicates the Dependabot grouping configuration from yiisoft/package-template so GitHub Actions updates are grouped into a single PR and Composer dependency updates are grouped into a single PR.

[Copilot]

Pull request overview

Note

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Adds Dependabot grouping rules so update PRs are consolidated (one for GitHub Actions, one for Composer), matching the referenced yiisoft/package-template configuration.

Changes:

• Group all GitHub Actions dependency updates into a single Dependabot PR.
• Group all Composer dependency updates into a single Dependabot PR.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (8d37240) to head (786c3d7).

Additional details and impacted files

@@             Coverage Diff             @@
##              master       #22   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       100       100           
===========================================
  Files             23        23           
  Lines            253       253           
===========================================
  Hits             253       253           

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