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/FormField.vue

@@ -0,0 +1,59 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { CircleAlert } from '@lucide/vue'
+import type { ControllerParams, FormField, RelationOption } from '../../api/types'
+import FieldRenderer from './FieldRenderer.vue'
+import { ownsLabel } from './registry'
+
+// One form row: label (600, red aria-hidden asterisk when required), the
+// control, the comment and the error line linked by aria-describedby.
+const props = defineProps<{
+  field: FormField
+  modelValue: unknown
+  errors?: string[]
+  labels?: RelationOption[]
+  source?: ControllerParams | null
+  /** Prefix for element ids, so two forms on a page never collide. */
+  idPrefix?: string
+}>()
+const emit = defineEmits<{ 'update:modelValue': [value: unknown] }>()
+
+const base = computed(() => `${props.idPrefix ?? 'field'}-${props.field.name}`)
+const controlId = computed(() => base.value)
+const commentId = computed(() => `${base.value}-comment`)
+const errorId = computed(() => `${base.value}-error`)
+const invalid = computed(() => (props.errors?.length ?? 0) > 0)
+const selfLabelled = computed(() => ownsLabel(props.field.type))
+const showComment = computed(() => !selfLabelled.value && !!props.field.comment)
+
+const describedBy = computed(() =>
+  [showComment.value || (selfLabelled.value && props.field.comment) ? commentId.value : '', invalid.value ? errorId.value : '']
+    .filter(Boolean)
+    .join(' '),
+)
+</script>
+
+<template>
+  <div class="flex min-w-0 flex-col gap-1.5" :data-field="field.name">
+    <label v-if="!selfLabelled" :for="controlId" class="font-semibold">
+      {{ field.label || field.name }}<span v-if="field.required" class="text-danger" aria-hidden="true"> *</span>
+    </label>
+    <FieldRenderer
+      :field="field"
+      :model-value="modelValue"
+      :control-id="controlId"
+      :invalid="invalid"
+      :described-by="describedBy"
+      :labels="labels"
+      :source="source"
+      @update:model-value="(value: unknown) => emit('update:modelValue', value)"
+    />
+    <p v-if="showComment" :id="commentId" class="text-[13px] text-muted">{{ field.comment }}</p>
+    <div v-if="invalid" :id="errorId" class="flex flex-col gap-0.5 text-[13px] text-danger">
+      <p v-for="(text, index) in errors" :key="index" class="flex items-center gap-1.5">
+        <CircleAlert :size="14" class="shrink-0" aria-hidden="true" />
+        <span>{{ text }}</span>
+      </p>
+    </div>
+  </div>
+</template>