Add GitHub Action workflow to support Admin API v2

[JakeSCahill]

This pull request introduces a new GitHub Actions workflow to automate the update of Admin API documentation in the docs repository whenever a new release is published. The workflow ensures that only the latest, non-draft, non-prerelease releases trigger the documentation update process.

New workflow for API documentation automation:

• Added .github/workflows/dispatch-api-docs.yml to dispatch an event to the docs repository (redpanda-data/api-docs) when a new, latest release is published.
• Workflow securely assumes an AWS role and fetches the ACTIONS_BOT_TOKEN from AWS Secrets Manager for authentication.
• Includes a step to verify that the release is the latest before dispatching the update event, preventing updates from drafts or prereleases.
• Uses the repository-dispatch action to notify the docs repository with the relevant release tag for documentation update.

Related: redpanda-data/api-docs#25

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.2.x
• v25.1.x
• v24.3.x

Release Notes

[Copilot]

Pull Request Overview

This PR adds automation for updating Admin API documentation by introducing a GitHub Actions workflow that triggers when new releases are published. The workflow ensures only the latest, non-draft, non-prerelease releases trigger documentation updates in the docs repository.

Key changes:

• New GitHub Actions workflow for automated API documentation updates
• AWS authentication integration for secure token retrieval
• Latest release verification to prevent unnecessary documentation updates