Case-insensitive sorting of child-resources

[dennisvang]

Use java.util.Comparator to sort child resources by title with String.CASE_INSENSITIVE_ORDER.

First sort case-insensitively, then sort lexicographically, to stabilize the result.

For example, instead of the default order (lexicographic) "A", "B", "a", "b", we now get "A", "a", "B", "b".

fixes #676

_{AI disclosure: Copilot (free) was used to review the PR, due to absence of human reviewers.}