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/components/form/fields/TextareaField.vue

@@ -0,0 +1,31 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { controlAttributes, controlClass, type FieldControlProps } from '../registry'
+
+const props = defineProps<FieldControlProps>()
+const emit = defineEmits<{ 'update:modelValue': [value: string] }>()
+
+// Winter textarea sizes mapped to rows; the design's Opis uses 4 (small).
+const rowsBySize: Record<string, number> = { tiny: 2, small: 4, large: 8, huge: 12, giant: 18 }
+
+const rows = computed(() => rowsBySize[props.field.size ?? ''] ?? 5)
+const text = computed(() => (props.modelValue === null || props.modelValue === undefined ? '' : String(props.modelValue)))
+const attrs = computed(() => controlAttributes(props.field))
+</script>
+
+<template>
+  <textarea
+    :id="controlId"
+    v-bind="attrs"
+    :name="field.name"
+    :rows="rows"
+    :value="text"
+    :required="field.required || undefined"
+    :aria-required="field.required ? 'true' : undefined"
+    :aria-invalid="invalid ? 'true' : undefined"
+    :aria-describedby="describedBy || undefined"
+    :class="controlClass(invalid)"
+    class="min-h-input resize-y py-2.5"
+    @input="emit('update:modelValue', ($event.target as HTMLTextAreaElement).value)"
+  />
+</template>