Modal dialog is missing an accessible name

[alegontarz]

Describe the bug

An ARIA dialog is rendered without an accessible name. The dialog element:
<ngb-modal-window role="dialog" tabindex="-1" aria-modal="true" class="d-block modal fade show">
does not provide a valid accessible name through aria-label, aria-labelledby, or title. As a result, screen reader users may not understand the purpose of the dialog when it opens.

To Reproduce

Steps to reproduce the behavior:

1. Open the search results page and click on All of DSpace
2. Inspect the modal element in the DOM or run an accessibility audit.
3. Check the ngb-modal-window element with role="dialog".

Expected behavior

The dialog has a valid accessible name that describes its purpose.

Suggested Fix

Prefer aria-labelledby tied to the modal heading, for example:

<ngb-modal-window
  role="dialog"
  tabindex="-1"
  aria-modal="true"
  aria-labelledby="modal-title"
  class="d-block modal fade show">
</ngb-modal-window>

<h2 id="modal-title">Filter settings</h2>