feat(webhook): Phase 4 — admin-ui /webhooks page

Routes:
- /webhooks (layout) → /webhooks/index (list) + /webhooks/$id (detail)
- nav link добавлен в __root.tsx между Outbox и Language switch

List page (webhooks.index.tsx):
- Table: name | URL | scope filter (colored dots) | dictionaries | status
- ScopeChips reuse SCOPE_DOT из lib/scope-style.ts (consistency с
  dictionaries scope coloring)
- Create dialog: name, URL, scope filter (MultiSelect), dictionary &
  event type (CSV inputs), description. Client-side validation
  (URL scheme, name required) дублирует server-side @Pattern.
- Secret reveal modal после create: warning + plaintext + copy button.
  Single-time view — после закрытия secret не получить, только rotate.

Detail page (webhooks.$id.tsx):
- Subscription metadata grid (URL, status, filters, masked secret,
  createdBy + timestamp)
- Action buttons: rotate-secret + delete (с confirmation)
- Delivery history table: outboxEventId | status badge (delivered/
  retrying/pending/dlq) | attempts | last attempt | HTTP code | error
- Pagination 50/page
- Status badges: delivered=success, retrying=warning, pending=neutral,
  dlq=error

API client (queries + mutations):
- 4 queries: subscriptions list, subscription by id, deliveries page,
  DLQ page (last unused в UI пока, но готов для admin DLQ tab)
- 4 mutations: create, update, delete, rotateSecret. Все invalidate
  правильные query keys.

i18n: 50 ключей × 2 локали (ru-RU + en-US) под webhooks.*

ordinis-admin-ui/src/routes/__root.tsx

@@ -44,6 +44,13 @@ function RootLayout() {
             >
               {t('nav.outbox')}
             </Link>
+            <Link
+              to="/webhooks"
+              className="text-carbon hover:text-ultramarain"
+              activeProps={{ className: 'text-ultramarain font-medium' }}
+            >
+              {t('nav.webhooks')}
+            </Link>
           </nav>
           <div className="ml-auto flex items-center gap-3">
             <LanguageSwitch