[Repo Assist] ci: add Dependabot config for GitHub Actions auto-updates

[github-actions]

🤖 This is an automated PR from Repo Assist.

Summary

Adds .github/dependabot.yml to enable Dependabot automatic dependency update PRs for GitHub Actions.

Why

The CI workflow currently uses several GitHub Actions (actions/checkout, actions/setup-dotnet, Particular/install-sql-server-action) that will drift behind current versions over time. Without Dependabot, these need to be updated manually.

This configuration:

• Weekly schedule — keeps action versions current without flooding the repo
• Grouped PRs — all GitHub Actions updates are bundled into a single PR per cycle, reducing notification noise
• Adds the enhancement label for easy filtering

Changes

• .github/dependabot.yml — new file (15 lines)

Notes

This only covers the github-actions ecosystem. The project uses paket for NuGet/F# package management (Dependabot's NuGet support is for PackageReference-based projects), so package updates are not included.

Note: PR #444 is in progress and also touches the CI workflow. This file is entirely new and does not conflict with any of those changes.

Test Status

Config-only addition — no source code, build scripts, or tests affected.

Generated by Repo Assist · ◷

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@346204513ecfa08b81566450d7d599556807389f

Generated by Repo Assist · ◷

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@346204513ecfa08b81566450d7d599556807389f

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Warning

🛡️ Protected Files

This was originally intended as a pull request, but the patch modifies protected files: .github/dependabot.yml.

These files may affect project dependencies, CI/CD pipelines, or agent behaviour. Please review the changes carefully before creating the pull request.

Click here to create the pull request once you have reviewed the changes

To route changes like this to a review issue instead of blocking, configure protected-files: fallback-to-issue in your workflow configuration.