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.vue

@@ -8,8 +8,12 @@ const inShell = computed(() => route.meta.shell === true)
 </script>
 
 <template>
+  <!-- Keyed by path, not full path: a new controller or record remounts its
+       view, while list query changes (search, sort, page) keep it. -->
   <AppShell v-if="inShell">
-    <RouterView />
+    <RouterView v-slot="{ Component, route: current }">
+      <component :is="Component" :key="current.path" />
+    </RouterView>
   </AppShell>
   <RouterView v-else />
 </template>