feat(admin): implement analytics and monitoring center

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

- Business Dashboard: revenue/orders/customers/AOV/top products/low stock/recent activity/warnings/completion% (Overview tab)
- Marketplace Health: real completion checks (images, SEO, categories, reviews, orders, translations, homepage, backend, performance) with clickable recommendations
- Product Analytics: top selling/most reviewed/worst rated/hidden/archived counts; top-viewed honestly marked Unknown (no view tracking exists)
- Customer Analytics: new/returning customers, average spend, retention - derived from real order data
- Search & Traffic tabs: honest 'Unknown - available after backend integration' placeholders, no fabricated numbers
- Recommendations engine: actionable cards (missing images/SEO/category, empty categories, incomplete homepage, unpublished static pages) linking to the relevant admin page
- System Monitoring: added real draft/publish/sync/backend-connectivity state from AdminDashboardFacade
- CSV export extended to top products and health checks; added print action
- New adminAnalytics.* and adminMarketplaceHealth.* i18n namespaces (en/ru/hy), no raw i18n keys
- Reused existing shared UI (app-table/app-badge/app-skeleton/app-empty-state) and content-health-widget completion-meter pattern - no new backend APIs, no storage changes

src/app/i18n/en.ts

@@ -1594,10 +1594,100 @@ export const en: Translations = {
   adminMonitoring: {
     eventsEmptyTitle: 'No events found',
     eventsEmptyDescription: 'Try a different category filter or search term.',
+    systemState: 'System state',
+    backendConnectivity: 'Backend',
+    connected: 'Connected',
+    loading: 'Loading',
+    draftState: 'Draft',
+    unsavedChanges: 'Unsaved changes',
+    noDraft: 'No draft',
+    lastSaved: 'Last saved',
+    lastPublished: 'Last published',
+    syncStatus: 'Sync',
   },
   adminAnalytics: {
     topProductsEmptyTitle: 'No product sales in this period',
     topProductsEmptyDescription: 'Try a wider date range.',
+    print: 'Print',
+    tabsLabel: 'Analytics sections',
+    tab: {
+      overview: 'Overview',
+      health: 'Health',
+      products: 'Products',
+      customers: 'Customers',
+      search: 'Search',
+      traffic: 'Traffic',
+      recommendations: 'Recommendations',
+    },
+    revenue: 'Revenue',
+    orders: 'Orders',
+    customers: 'Customers',
+    avgOrderValue: 'Avg. Order Value',
+    conversion: 'Conversion',
+    completionPercent: 'Completion',
+    unknown: 'Unknown',
+    salesChart: 'Sales',
+    quantitySold: 'Qty sold',
+    lowStock: 'Low stock',
+    lowStockEmptyTitle: 'No low-stock products',
+    quantity: 'Quantity',
+    status: 'Status',
+    recentActivity: 'Recent activity',
+    recentActivityEmptyTitle: 'No recent activity',
+    activityDraftSaved: 'Draft saved',
+    activityPublished: 'Published',
+    warnings: 'Warnings',
+    topViewed: 'Top viewed',
+    hiddenProducts: 'Hidden products',
+    archivedProducts: 'Archived products',
+    mostReviewed: 'Most reviewed',
+    worstRated: 'Worst rated',
+    noReviewedProducts: 'No reviewed products yet',
+    reviewCount: 'Reviews',
+    avgRating: 'Avg. rating',
+    newCustomers: 'New customers',
+    returningCustomers: 'Returning customers',
+    averageSpend: 'Average spend',
+    retention: 'Retention',
+    searchAnalytics: 'Search analytics',
+    trafficAnalytics: 'Traffic',
+    availableAfterBackend: 'Available after backend integration.',
+    pendingBackend: 'Pending backend',
+    pendingBackendHint: 'No search-query tracking exists yet.',
+    funnelsHeatmaps: 'Funnels & heatmaps',
+    visitors: 'Visitors',
+    products: 'Products',
+    categories: 'Categories',
+  },
+  adminMarketplaceHealth: {
+    title: 'Marketplace health',
+    complete: 'complete',
+    recommendationsTitle: 'Recommendations',
+    recommendNone: 'Everything looks good.',
+    checkImages: 'Products have images',
+    checkSeo: 'Products have SEO metadata',
+    checkCategories: 'Categories have products',
+    checkReviews: 'Reviews are moderated',
+    checkOrders: 'Orders are processed',
+    checkTranslations: 'Translations are complete',
+    checkHomepage: 'Homepage is configured',
+    checkBackend: 'Backend connectivity',
+    checkPerformance: 'Performance',
+    recommendImages: 'Add images to products missing them',
+    recommendImagesCount: 'Products without images hurt conversion.',
+    recommendSeo: 'Add SEO metadata to products missing it',
+    recommendSeoCount: 'Missing SEO titles/descriptions hurt search visibility.',
+    recommendCategory: 'Assign a category to uncategorized products',
+    recommendCategoryCount: 'Products without a category are harder to discover.',
+    recommendEmptyCategories: 'Categories without products',
+    recommendEmptyCategoriesCount: 'Consider merging or removing empty categories.',
+    recommendHomepage: 'Homepage is incomplete',
+    recommendStaticPages: 'Static pages are unpublished',
+    severity: {
+      info: 'Info',
+      warning: 'Warning',
+      critical: 'Critical',
+    },
   },
   adminShell: {
     skipToContent: 'Skip to content',