Files uploaded with some symbols not accessible

Uploaded file named "Års.pdf" and link created is not accessible from page.

Reproduce the upload in the Grav Admin Plugin using the filename "Års.pdf" and inspect the generated page link. Trace the upload and link-generation entry points, then verify that the uploaded file opens successfully from the page and add a regression test if the repository provides a relevant test location.

Written by the indexing model from the issue text.