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/admin/dashboard/components/admin-dashboard-card.component.html

@@ -0,0 +1,23 @@
+<article class="dashboard-card" [class.dashboard-card--error]="status === 'error'" [class.dashboard-card--pending]="status === 'pending-backend'">
+  <header class="dashboard-card__header">
+    <span class="dashboard-card__icon" *ngIf="icon" aria-hidden="true">{{ icon }}</span>
+    <h3 class="dashboard-card__title">{{ title }}</h3>
+  </header>
+
+  <div class="dashboard-card__body">
+    <ng-container [ngSwitch]="status">
+      <div class="dashboard-card__skeleton" *ngSwitchCase="'loading'"></div>
+
+      <p class="dashboard-card__muted" *ngSwitchCase="'empty'">{{ 'dashboard.stateEmpty' | translate }}</p>
+
+      <p class="dashboard-card__muted dashboard-card__muted--error" *ngSwitchCase="'error'">{{ 'dashboard.stateError' | translate }}</p>
+
+      <p class="dashboard-card__muted" *ngSwitchCase="'pending-backend'">{{ 'dashboard.statePendingBackend' | translate }}</p>
+
+      <ng-container *ngSwitchDefault>
+        <p class="dashboard-card__value">{{ value }}</p>
+        <p class="dashboard-card__subtitle" *ngIf="subtitle">{{ subtitle }}</p>
+      </ng-container>
+    </ng-container>
+  </div>
+</article>