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/features/project-editor/facade/project-editor.facade.ts

@@ -30,6 +30,7 @@ export class ProjectEditorFacade {
     status: 'draft',
     lastSavedBootstrap: null,
     lastSavedAt: null,
+    lastPublishedAt: null,
     draftRestored: false,
   });
 
@@ -40,6 +41,7 @@ export class ProjectEditorFacade {
   readonly homepageWidgets = computed(() => this.homepagePage()?.sections.flatMap(section => section.widgets.map(widget => ({ sectionId: section.id, sectionType: section.type, widget }))) ?? []);
   readonly status = computed(() => this.state().status);
   readonly lastSavedAt = computed(() => this.state().lastSavedAt);
+  readonly lastPublishedAt = computed(() => this.state().lastPublishedAt);
   readonly draftRestored = computed(() => this.state().draftRestored);
   readonly validationIssues = computed(() => {
     const current = this.bootstrap();
@@ -182,6 +184,7 @@ export class ProjectEditorFacade {
       lastSavedBootstrap: JSON.parse(JSON.stringify(current)),
       originalBootstrap: JSON.parse(JSON.stringify(current)),
       lastSavedAt: savedAt,
+      lastPublishedAt: savedAt,
     }));
     return true;
   }