ci: publish openapi to scalar, sync version

[alexfreska]

• Workflow for publishing the openapi spec when the file changes on master or via manual trigger.
  • Note: this step will throw an error until tomorrow. I reported an issue with this API to the scalar team and they said it would be fixed in the next release (1-2 days).
• Workflow for syncing the openapi spec version field to the repo latest release version. When the versions are out of sync this workflow will open a PR.
  • Depends on add sync openapi version workflow workflows#17 being merged.

[Copilot]

Pull Request Overview

This PR adds a GitHub Actions workflow to automatically publish the OpenAPI specification to Scalar Registry when changes are made to the openapi.yml file or when manually triggered.

• Adds automated publishing of OpenAPI spec to Scalar Registry
• Configures workflow to trigger on openapi.yml changes to master branch
• Enables manual workflow dispatch for on-demand publishing

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[ChrisSchinnerl]

Could you also update the version in the openapi spec to match the latest released renterd version?

[alexfreska]

I added another shared workflow for that, I'll add it to this PR. SiaFoundation/workflows#17