forward cache-status header in images middleware

[Roshan-Pawar]

Closes # 7962

Fix: Forward Cache-Status header in images middleware

The images middleware maintains an explicit allowlist of response headers forwarded from the backend.
The Cache-Status header (RFC 9211) was missing from this list, causing it to be stripped from responses.

[mister-roboto]

@Roshan-Pawar you need to sign the Plone Contributor Agreement to merge this pull request.

Learn about the Plone Contributor Agreement: https://plone.org/foundation/contributors-agreement

If you have already signed the agreement, please allow a week for your agreement to be processed.
Once it is processed, you will receive an email invitation to join the plone GitHub organization as a Contributor.

If after a week you have not received an invitation, then please contact agreements@plone.org.

[boring-cyborg]

Caution

The Volto Team has suspended its review of new pull requests from first-time contributors until the release of Plone 7, which is preliminarily scheduled for the second quarter of 2026.
Read details.

Thanks for submitting your first pull request! You are awesome! 🤗

If you haven't done so already, read
Plone's Code of Conduct,
Contributing to Plone,
First-time contributors, and
Contributing to Volto,
as this will greatly help the review process.

Welcome to the Plone community! 🎉