feat(admin): sprint 19 admin dashboard, routing, i18n

- Add admin dashboard feature (models/gateway/facade/components/page)
- Wire admin/products routes and backoffice coming-soon placeholders
- Add lastPublishedAt to ProjectEditorFacade/state
- Add dashboard i18n keys (en/ru/hy) and docs/ADMIN.md

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

src/app/i18n/translations.ts

@@ -510,6 +510,8 @@ export interface Translations {
     validationMissingWidget: string;
     validationDuplicateNavLinks: string;
     validationInvalidColors: string;
+    validationMissingTranslations: string;
+    validationInvalidLayouts: string;
     statusDraft: string;
     statusPublished: string;
     unsavedChanges: string;
@@ -528,6 +530,52 @@ export interface Translations {
     confirmResetDraft: string;
     confirmResetSection: string;
   };
+  dashboard: {
+    title: string;
+    subtitle: string;
+    cardMarketplaceStatus: string;
+    cardProjectName: string;
+    cardCurrentTheme: string;
+    cardLanguages: string;
+    cardCategoriesCount: string;
+    cardProductsCount: string;
+    cardOrders: string;
+    cardRevenue: string;
+    cardLastPublish: string;
+    cardLastDraftSave: string;
+    cardBootstrapVersion: string;
+    cardActiveLayout: string;
+    cardEnabledWidgets: string;
+    stateLoading: string;
+    stateEmpty: string;
+    stateError: string;
+    statePendingBackend: string;
+    never: string;
+    quickActionsTitle: string;
+    actionEditProject: string;
+    actionCategories: string;
+    actionProducts: string;
+    actionStaticPages: string;
+    actionTransactions: string;
+    actionOrders: string;
+    actionMediaLibrary: string;
+    actionPreviewMarketplace: string;
+    activityTitle: string;
+    activityEmpty: string;
+    activityDraftSaved: string;
+    activityPublished: string;
+    healthTitle: string;
+    healthAllClear: string;
+    healthBootstrapValid: string;
+    healthConfigurationValid: string;
+    healthMissingTranslations: string;
+    healthInvalidColors: string;
+    healthInvalidWidgetReferences: string;
+    healthInvalidLayouts: string;
+    comingSoonTitle: string;
+    comingSoonDescription: string;
+    backToDashboard: string;
+  };
   staticPages: {
     notFound: string;
     backHome: string;