Add CDN publish back temporarily

[robbecker-wf]

Summary

We moved to Github Actions but need to fix some things internal to Workiva before being able to remove Dockerfile and skynet.yaml completely. This undoes those removals and drops older versions of Dart from CI.

[aviary-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure

• Verify aviary.yaml coverage of security relevant code

  Questions or Comments? Reach out on Slack: #support-infosec.

[robbecker-wf]

@Workiva/release-management-p :letsroll: