chore: add dependabot configuration for GitHub Actions updates

[eloi010]

Description

Adding Dependabot updates for GitHub Actions.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Note

Low Risk
Only adds Dependabot configuration; no production code or runtime behavior changes, but it will create automated dependency update PRs for workflow actions.

Overview
Adds a new .github/dependabot.yml to enable weekly Dependabot updates for GitHub Actions used in workflows.

Updates are limited to 5 open PRs, assigned/labeled consistently, use a deps(actions) commit prefix, group core (actions/*, github/*) vs third-party action updates for minor/patch bumps, and enforce a 7-day cooldown between update PRs.

^{Written by Cursor Bugbot for commit 75a9951. This will update automatically on new commits. Configure here.}

[Copilot]

Pull request overview

This PR adds Dependabot automation for GitHub Actions dependency updates. The configuration enables weekly automated updates on Mondays at 03:00 UTC, with intelligent grouping of minor and patch updates to reduce PR noise.

Changes:

• Adds .github/dependabot.yml to enable automated GitHub Actions dependency updates

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