🐛(backend) compute ancestor_links in get_abilities if needed

The refactor made in the tree view caching the ancestors_links to not
compute them again in the document.get_abilities method lead to a bug.
If the get_abilities method is called without ancestors_links, then they
are computed on all the ancestors but not from the highest readable
ancestor for the current user. We have to compute them with this
constraint.

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to
 
 - ♻️(frontend) Integrate UI kit #783
 
+## Fixed
+
+- 🐛(backend) compute ancestor_links in get_abilities if needed #725
+
 ## [2.6.0] - 2025-03-21
 
 ## Added