Describe the bug

If I share a folder via public link and someone opens it, the language of the sharing page will be set according to the browser's preference (the Accept-Language header). But at the same time, the html lang attribute is always set to en. This could lead to strange phenomenons: e. g. a screen reader reading German text with a strong English accent – because it relies on a lang attribute which doesn't fit the actual language.

Steps to reproduce

1. Share a folder or file via public link
2. Access the share in a different browser where you're not logged in (set the browser's preferred language to something other than English)
3. Open developer tools to see that the lang attribute and the actual language of the page mismatch:
   

Expected behavior

The actual language of the page should always change together with the html lang global attribute. This is working fine while being logged in and changing the language manually in the settings, …

Actual behavior

… but it doesn't work with public shares – and people who are not logged in.

Setup

- Web version: 11.3.1
- oCIS version: 7.1.2 Community
- browser: Google Chrome 134.0.6998.165

podman run --rm -it -v ocis-config:/etc/ocis/ docker.io/owncloud/ocis:7 init
podman run --rm -p 9200:9200 -v ocis-config:/etc/ocis -v ocis-data:/var/lib/ocis -e IDM_CREATE_DEMO_USERS=true   docker.io/owncloud/ocis:7

Additional context

This might relate to #9288