chore: add dependabot configuration

[UserMandhapati]

Enable weekly dependency updates for pip and GitHub Actions to ensure security and stability.

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Note

Low Risk
Low risk: this only adds repository metadata for automated dependency update PRs and does not change runtime code paths.

Overview
Adds .github/dependabot.yml to enable weekly Dependabot update PRs for pip dependencies and github-actions workflows.

^{Written by Cursor Bugbot for commit afe2f5b. This will update automatically on new commits. Configure here.}