feat(l1): admin L1 category settings page + route + settings card

New owner-gated pages/account/L1CategoriesPage.tsx: checkbox list of available
categories toggling enabled via l1Api.getCategories/setCategories, plus a read-only
'always excluded (safety)' hard-floor list. Registered lazy route /account/l1-categories
(ProtectedRoute requiredRole=owner) and an 'L1 AI build categories' card in the
AccountSettingsPage owner section. tsc -b + eslint clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/router.tsx

@@ -114,6 +114,7 @@ const IntegrationsPage = lazyWithRetry(() => import('@/pages/account/Integration
 const BrandingSettingsPage = lazyWithRetry(() => import('@/pages/account/BrandingSettingsPage'))
 const BillingPage = lazyWithRetry(() => import('@/pages/account/BillingPage'))
 const SelectPlanPage = lazyWithRetry(() => import('@/pages/account/SelectPlanPage'))
+const L1CategoriesPage = lazyWithRetry(() => import('@/pages/account/L1CategoriesPage'))
 
 /** Wraps a lazy-loaded page with Suspense + ErrorBoundary */
 function page(Component: React.LazyExoticComponent<React.ComponentType>) {
@@ -363,6 +364,14 @@ export const router = sentryCreateBrowserRouter([
               </ProtectedRoute>
             ),
           },
+          {
+            path: 'l1-categories',
+            element: (
+              <ProtectedRoute requiredRole="owner">
+                {page(L1CategoriesPage)}
+              </ProtectedRoute>
+            ),
+          },
           {
             path: 'chat-retention',
             element: (