Issue #3595612: name the item on the record view page title

Follow-up to #3595596. That issue gave the record/file add and edit form titles item-naming titles, but the record view page (route pdv.record.view) is a separate route that was missed -- it still showed the static "Structured data".

This gives pdv.record.view a _title_callback that names the item: the custom label if set, else the kind label (e.g. "Civil status" / "État civil"). The shared label resolution (decrypt custom label, fall back to kind) is refactored into one itemDisplayLabel() helper used by the add, edit, and view callbacks.

phpcs + phpstan clean; confirmed locally (the view page now reads "Etat civil").