feat(17-01): repeater field type and the dependent dropdown save recheck

- cabana: type repeater with nested form.fields (text, textarea, number,
  checkbox, switch, dropdown, richeditor), prompt, minItems, maxItems,
  titleFrom; groups, style, nested repeaters and other types fail boot
- rows decoded before projection: only nested keys, coerced scalars,
  per-row required (field.index.nested), row bounds; ProjectWritableFields
  exempts repeater lists only, nestedValue unchanged
- nested richeditor values sanitized with notices under the row path
- dependent dropdowns rechecked on save, top level and per row; null when
  the sibling takes no choice, 422 form.dependent_invalid otherwise
- dependent-options accepts repeater.field; schema carries RepeaterForm
- backend lang repeater.max_items, repeater.min_items,
  form.dependent_invalid; TestCompanionsRepeaterSmoke; docs

modules/phrasebook/backend/lang/en/lang.yaml

@@ -102,6 +102,7 @@ form:
   action_done: Action completed.
   action_stale: This action no longer applies to this record. The page has been refreshed.
   forbidden: You do not have permission to make this change. Nothing was saved.
+  dependent_invalid: Choose one of the listed options.
 relation:
   add: Add
   link: Link
@@ -334,3 +335,6 @@ richeditor:
     one: ":count HTML comment was removed"
     other: ":count HTML comments were removed"
   markup_changed: The HTML filter changed some markup.
+repeater:
+  max_items: Remove items until there are at most :max.
+  min_items: Add items until there are at least :min.

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

@@ -112,6 +112,7 @@ form:
   action_done: Akcja została wykonana.
   action_stale: Ta akcja nie dotyczy już tego rekordu. Strona została odświeżona.
   forbidden: Nie masz uprawnień do wprowadzenia tej zmiany. Nic nie zostało zapisane.
+  dependent_invalid: Wybierz jedną z dostępnych opcji.
 relation:
   add: Dodaj
   link: Dołącz
@@ -362,3 +363,6 @@ richeditor:
     many: "Usunięto :count komentarzy HTML"
     other: "Usunięto :count komentarza HTML"
   markup_changed: Filtr HTML zmienił część znaczników.
+repeater:
+  max_items: Usuń pozycje, aby zostało ich najwyżej :max.
+  min_items: Dodaj pozycje, aby było ich co najmniej :min.