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/state/useToasts.ts

@@ -0,0 +1,52 @@
+// Global toast queue (design: State Management). Toasts outlive route
+// changes because AppShell mounts the renderer, so "Zapisz i zamknij" can
+// show its toast on the list it returns to.
+import { readonly, ref } from 'vue'
+
+export type ToastTone = 'success' | 'danger'
+
+export interface ToastItem {
+  id: number
+  text: string
+  tone: ToastTone
+}
+
+/** Auto-dismiss delay in milliseconds (design: about 4 s). */
+export const TOAST_TIMEOUT = 4000
+
+const items = ref<ToastItem[]>([])
+const timers = new Map<number, ReturnType<typeof setTimeout>>()
+let nextId = 1
+
+export const toasts = readonly(items)
+
+export function showToast(text: string, tone: ToastTone = 'success'): number {
+  const id = nextId++
+  items.value = [...items.value, { id, text, tone }]
+  timers.set(
+    id,
+    setTimeout(() => dismissToast(id), TOAST_TIMEOUT),
+  )
+  return id
+}
+
+export function dismissToast(id: number): void {
+  const timer = timers.get(id)
+  if (timer !== undefined) {
+    clearTimeout(timer)
+    timers.delete(id)
+  }
+  items.value = items.value.filter((item) => item.id !== id)
+}
+
+export function clearToasts(): void {
+  for (const timer of timers.values()) {
+    clearTimeout(timer)
+  }
+  timers.clear()
+  items.value = []
+}
+
+export function useToasts() {
+  return { toasts, showToast, dismissToast, clearToasts }
+}