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 94.66%. Comparing base (1a60ff6) to head (8b21b6e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #36   +/-   ##
=======================================
  Coverage   94.66%   94.66%           
=======================================
  Files           9        9           
  Lines         675      675           
  Branches       97       97           
=======================================
  Hits          639      639           
  Misses         36       36           

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