feat(10-03): open, edit and save a record with toast and 422 feedback

- The SPA loads the backend::lang bundle before /auth/me, sets the
  document language from meta.locale and renders plural messages with
  Intl.PluralRules; interpolate mirrors phrasebook for :name/:Name/:NAME
- Create and record routes; mapWinterUrl maps recordUrl and redirects
  onto the controller's list, create and record routes only
- List rows open their record; FormView loads the form schema and the
  record, shows context-allowed fields in the span grid, saves values
  keyed by field name and toasts the resolved saved message
- A 422 puts each message under its field (aria-invalid,
  aria-describedby), shows the plural banner, focuses the first invalid
  field in schema order and clears a field's error on change
- The D-05 registry maps text, textarea, number and dropdown; any other
  type renders the unsupported-field box with the type in DM Mono
- The admin OpenAPI document declares the write request bodies
  (AdminRecord, AdminIDsRequest) and the list filter query as a
  deepObject, so the typed client can send them
- New backend::lang form.load_failed key; boardwalk/dist rebuilt

admin/src/app/router.ts

@@ -4,6 +4,7 @@ import { currentUser } from '../state/useAuth'
 import { homePath } from '../state/useNavigation'
 import LoginView from '../views/LoginView.vue'
 import ListView from '../views/ListView.vue'
+import FormView from '../views/FormView.vue'
 import NotFoundView from '../views/NotFoundView.vue'
 
 declare module 'vue-router' {
@@ -43,6 +44,8 @@ export function createAdminRouter(history: RouterHistory = createWebHistory(runt
         beforeEnter: () => homePath() ?? true,
       },
       { path: '/:vendor/:plugin/:controller', name: 'list', component: ListView, meta: { shell: true } },
+      { path: '/:vendor/:plugin/:controller/create', name: 'create', component: FormView, meta: { shell: true } },
+      { path: '/:vendor/:plugin/:controller/:id(\\d+)', name: 'record', component: FormView, meta: { shell: true } },
       { path: '/:pathMatch(.*)*', name: 'not-found', component: NotFoundView, meta: { shell: true } },
     ],
   })