feat(admin): analytics dashboard

Sprint 27.

New features/admin/analytics/ module + net-new /:lang/backoffice/analytics
route + Dashboard Quick Action.

- revenue/orders/avg-order-value/sales-over-time/top-products computed by
  composing AdminOrdersLocalGateway (Sprint 23's seeded mock orders) - real
  aggregation over mock data, not a separate fabricated dataset
- products/categories counts from AdminProductsLocalGateway/
  AdminCategoriesLocalGateway
- visitors/funnels/heatmaps render pending-backend badges (no analytics
  pipeline exists anywhere in this system) rather than fabricated numbers,
  same convention as the Sprint 19 dashboard's pre-Sprint-23 Orders/Revenue
  cards
- plain div-bar chart (no charting library), 7/30/90-day range toggle,
  CSV export

docs/ADMIN.md + docs/BACKEND.md (new item 16) updated.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/app.routes.ts

@@ -116,6 +116,10 @@ const coreRoutes: Routes = [
         path: 'monitoring',
         loadComponent: () => import('./features/admin/monitoring/pages/admin-monitoring-page.component').then(m => m.AdminMonitoringPageComponent)
       },
+      {
+        path: 'analytics',
+        loadComponent: () => import('./features/admin/analytics/pages/admin-analytics-page.component').then(m => m.AdminAnalyticsPageComponent)
+      },
       { path: '**', redirectTo: 'dashboard' }
     ]
   },