chore: add engineering standards (dependabot)

[nikzen]

Automated rollout from engineering-standards.

Base (always included):

• .github/dependabot.yml – automated dependency updates (Dependabot)
• Ecosystems: github-actions, python
• Grouped PRs: major updates separate from minor+patch
• Cooldown: 14 days

Detected scope: python

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.61%. Comparing base (119f8dd) to head (8fec667).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #124   +/-   ##
=======================================
  Coverage   97.61%   97.61%           
=======================================
  Files           7        7           
  Lines         712      712           
  Branches      104      104           
=======================================
  Hits          695      695           
  Misses         17       17           

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