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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Updates Dependabot configuration to group dependency updates similarly to yiisoft/package-template, reducing PR noise and enabling scheduled updates.

Changes:

• Enable grouped updates for GitHub Actions so all action bumps land in a single PR.
• Enable grouped updates for Composer so all dependency bumps land in a single PR.
• Adjust schedules (Actions weekly; Composer daily) and add ignore rule(s).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.73%. Comparing base (b7461a6) to head (bd947d9).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #115   +/-   ##
=========================================
  Coverage     93.73%   93.73%           
  Complexity      155      155           
=========================================
  Files             4        4           
  Lines           335      335           
=========================================
  Hits            314      314           
  Misses           21       21           

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