feat: enhance release workflow to support dynamic platform selection for Docker builds

[masmuss]

This pull request updates the release-image.yml GitHub Actions workflow to make the target image platforms configurable and more flexible. The main improvement is allowing users to specify custom platforms for image builds, with sensible defaults and backward compatibility.

Key workflow improvements:

Platform configuration enhancements:

• Added a new platforms input to the workflow, allowing users to specify a comma-separated list of target platforms (e.g., linux/amd64,linux/arm64).
• Introduced the DEFAULT_IMAGE_PLATFORMS environment variable to centralize the default platform values.
• Added a new "Resolve image platforms" step that determines the final list of platforms to use, prioritizing user input (when triggered via workflow_dispatch), and falling back to defaults if not provided.

Build step updates:

• Updated the Docker build step to use the dynamically resolved platforms value instead of a hardcoded list, ensuring the workflow respects user input or defaults as appropriate.

[github-actions]

🎉 This PR is included in version 1.2.0 🎉

The release is available on GitHub release

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