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/en/lang.yaml

@@ -94,6 +94,11 @@ relation:
   candidates_range: ":from–:to of :total"
   no_candidates: There are no records to add.
   load_failed: The linked records could not be loaded.
+  child_load_failed: The record could not be loaded. Close this window and try again.
+  child_gone: This record no longer exists. The list has been refreshed.
+  next: Next
+  back: Back
+  pending_note: Changes in this section are saved together with the record.
 settings:
   title: Settings
   empty: No settings are available.