Translating pages that include an image don't work

[JeroenJADS]

Issue Summary

Upon translating a page from EN to Dutch that has an image uploaded, Wagtail tries to call an url "en/cms/api/main/images/1/", which is called the Images Admin Api but is unauthorized to do so. This in turn leads to an error in wagtail-localize.js since the image can not be found.

Steps to Reproduce

1. Add a page in the original Wagtail Language
2. Add an image field and upload any image
3. Translate the page, select the desired language and hit confirm
4. The next page will throw the 2 errors above.
5. The page will load, but the translation editor will have been broken.

Technical details

• Wagtail 6.2
• Django version: 5.0.4
• Browser version: Chrome 129.

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[zerolab]

We need a bit more information, like how you've configured your URLs for i18n