Add Dependabot for Pip & GitHub Actions

[Borda]

What does this PR do?

Motivation

Preventing outdated dependencies and CI workflows from drifting is critical to maintain build stability and security. Automating updates reduces manual overhead, avoids unexpected breakages, and ensures our Python ecosystem and CI actions remain compatible without overflowing open PR counts.

Changes

Introduce dependabot.yml to enable:

• Monthly pip dependency updates (limit 5 open PRs)
• Weekly GitHub Actions updates grouped into a single PR (limit 1 open PR) to keep workflows current without exploding PR counts.

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in GitHub issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85%. Comparing base (a7b5910) to head (225e94f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #541   +/-   ##
===================================
  Coverage    85%    85%           
===================================
  Files        38     38           
  Lines      2901   2901           
===================================
  Hits       2479   2479           
  Misses      422    422           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.