chore: add engineering standards (dependabot)

[nikzen]

Automated rollout from engineering-standards.

Base (always included):

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

Detected scope: generic

[CLAassistant]

All committers have signed the CLA.

[github-actions]

* fa8266fd96e60bdac3bca08fa7a2a2827835b6e4 chore: add engineering standards (dependabot, generic)
|   - Error: Could not find a certificate with BDE15DDCE302F9E417F426D9A575DDEB3DB7D052 in the policy file
* 57b383862ba81dfa265bb33d492e2bbcbc96891d Revert "chore(docker): use clean_registry in step `Create manifest list and push`"
    - Trust root.

Failed to authenticate commits.

Error: Could not verify commits 57b383862ba81dfa265bb33d492e2bbcbc96891d..fa8266fd96e60bdac3bca08fa7a2a2827835b6e4

Caused by:
    0: While verifying commit fa8266fd96e60bdac3bca08fa7a2a2827835b6e4
    1: Could not find a certificate with BDE15DDCE302F9E417F426D9A575DDEB3DB7D052 in the policy file