feat(10-02): backend strings, controller messages and declarative toolbar

- phrasebook ships the backend::lang admin strings (pl, en) with CLDR
  plural maps, loads them as namespace backend, applies
  pact.HasLangOverrides trees (lang/<locale>/<namespace>/<group>.yaml)
  after every namespace, and fails activation when a backend key cannot
  convert to plural forms
- Translator.Forms, Bundle, Resolved and Has serve keys as CLDR form maps
- Public GET /lang returns every backend::lang key for the request
  locale over the fallback locale, Cache-Control no-cache
- config_list, config_form and config_relation accept a strict messages
  block; omitted keys take framework defaults, schemas serve every message
  as CLDR forms, and activation fails on a missing phrase key
- toolbar.buttons is an ordered [create, delete] list; the Winter string
  form, duplicates, unknown actions and delete without showCheckboxes fail
  at boot, and create is dropped when the controller has no form
- Form schema serves the raw Winter redirects; scaffold emits the list
  syntax; form and relation schema routes are typed in the admin OpenAPI

cabana/schema_types.go

@@ -1,6 +1,9 @@
 package cabana
 
-import "encoding/json"
+import (
+	"context"
+	"encoding/json"
+)
 
 // ListSort is the compiled default sort. Direction is exactly asc or desc.
 type ListSort struct {
@@ -68,11 +71,20 @@ type ListSchema struct {
 	Filters          []ListFilter `json:"filters"`
 	RowActions       []RowAction  `json:"rowActions"`
 	BulkActions      []BulkAction `json:"bulkActions"`
-	Meta             *FormMeta    `json:"meta,omitempty"`
+	// Messages is the list's copy (D-13). The cached schema carries each
+	// phrase key as its own form; a response resolves them in its locale.
+	Messages *ListMessages `json:"messages"`
+	Meta     *FormMeta     `json:"meta,omitempty"`
+
+	messageKeys listMessageKeys
 }
 
 // MarshalJSON keeps omitted collections as arrays so a partial copy cannot emit null.
 func (s ListSchema) MarshalJSON() ([]byte, error) {
+	if s.Messages == nil {
+		keys := localizeMessages[listMessageKeys, ListMessages](context.Background(), nil, s.listMessageKeySet())
+		s.Messages = &keys
+	}
 	type alias ListSchema
 	out := alias(s)
 	if out.PerPageOptions == nil {
@@ -102,6 +114,9 @@ type FormSchema struct {
 	Name       string      `json:"name,omitempty"`
 	ModelClass string      `json:"modelClass,omitempty"`
 	Fields     []FormField `json:"fields"`
+
+	messageKeys formMessageKeys
+	redirects   FormRedirects
 }
 
 // FormView is one request's localized form, including the locale actually used.
@@ -109,7 +124,25 @@ type FormView struct {
 	Name       string      `json:"name,omitempty"`
 	ModelClass string      `json:"modelClass,omitempty"`
 	Fields     []FormField `json:"fields"`
-	Meta       FormMeta    `json:"meta"`
+	// Messages is the form's copy resolved in the request locale (D-13).
+	Messages FormMessages `json:"messages"`
+	// Redirects are the raw Winter config_form.yaml targets; the SPA maps
+	// them onto its routes.
+	Redirects FormRedirects `json:"redirects"`
+	Meta      FormMeta      `json:"meta"`
+}
+
+// FormRedirects are config_form.yaml defaultRedirect, create.* and update.*.
+type FormRedirects struct {
+	Default string       `json:"default"`
+	Create  FormRedirect `json:"create"`
+	Update  FormRedirect `json:"update"`
+}
+
+// FormRedirect is one Winter redirect pair.
+type FormRedirect struct {
+	Redirect      string `json:"redirect"`
+	RedirectClose string `json:"redirectClose"`
 }
 
 // FormMeta reports the locale selected for a schema response.