feat(12.2-04): edit related records in modals and defer relation work on new records

- RelationManager renders create/link/delete/unlink in declared order with
  one primary, opens the child modal (update or view form) or the pivot
  modal on row click, and deletes selected children behind a busy confirm
- RelationChildModal creates and edits children with its own session key
  (X-Child-Session-Key) so uploads and dates work inside it
- RelationPivotModal edits link details; the picker links one record with
  its pivot values when the relation has a pivot form
- deferrable managers render on the create screen with owner id 0, the
  form's X-Session-Key and the pending note, and mark the form dirty
- the registry resolves RelationManager lazily (child forms close an
  import cycle); DataTable gains openable rows and a trailing cell
- relation lang keys in en and pl; rebuilt boardwalk dist

modules/phrasebook/backend/lang/pl/lang.yaml

@@ -102,6 +102,11 @@ relation:
   candidates_range: ":from–:to z :total"
   no_candidates: Brak rekordów do dodania.
   load_failed: Nie udało się wczytać powiązanych rekordów.
+  child_load_failed: Nie udało się wczytać rekordu. Zamknij to okno i spróbuj ponownie.
+  child_gone: Ten rekord już nie istnieje. Lista została odświeżona.
+  next: Dalej
+  back: Wstecz
+  pending_note: Zmiany w tej sekcji zostaną zapisane razem z rekordem.
 settings:
   title: Ustawienia
   empty: Brak dostępnych ustawień.