chore: add engineering standards (dependabot)

[nikzen]

Automated rollout from engineering-standards.

Base (always included):

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

Detected scope: rust

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.16%. Comparing base (0fca161) to head (3365905).

Additional details and impacted files

@@          Coverage Diff          @@
##            main     #91   +/-   ##
=====================================
  Coverage   3.16%   3.16%           
=====================================
  Files        888     888           
  Lines      36905   36905           
=====================================
  Hits        1168    1168           
  Misses     35737   35737           

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