fix(action): explicitly add package-manager for astro

[debloper]

https://github.com/debloper/piosk/actions/runs/16654165831/job/47134671674

Run withastro/action@v4
Run len=`echo $INPUT_PM | wc -c`
No lockfile found.
Please specify your preferred "package-manager" in the action configuration.
Error: Process completed with exit code 1.

[Copilot]

Pull Request Overview

This PR fixes a GitHub Actions workflow failure by explicitly specifying the package manager for the Astro action. The workflow was failing because no lockfile was found and the action couldn't automatically detect the package manager to use.

• Adds explicit package-manager: npm configuration to the withastro/action@v4 step
• Resolves the "No lockfile found" error that was causing the workflow to fail