fix(ui): replace native confirm()/alert() with shared dialogs and toasts

New app-confirm-dialog (wraps existing app-dialog + app-button) replaces
every native confirm() across media library bulk-delete, static pages
editor (delete/bulk-delete), builder save-bar (publish/reset-draft),
project-editor-page (reset-section), homepage/languages/widgets sections
(remove block/language/widget), and cart (clear-cart).

Cart's native alert() calls (delivery/terms validation, email send
success/failure) now route through the existing UserNotificationService
toast pipeline instead.

No native confirm()/alert()/prompt() remain in production UI.

src/app/features/backoffice/media/media-library-page.component.html

@@ -127,4 +127,17 @@
       <app-button variant="danger" (click)="proceedDelete()">{{ 'mediaLibrary.confirm' | translate }}</app-button>
     </div>
   </app-dialog>
+
+  <app-dialog
+    [open]="bulkDeleteConfirmOpen()"
+    [titleText]="'mediaLibrary.deleteConfirmTitle' | translate"
+    size="sm"
+    (closed)="bulkDeleteConfirmOpen.set(false)"
+  >
+    <p>{{ 'mediaLibrary.bulkDeleteConfirm' | translate }}</p>
+    <div class="media-page__dialog-actions">
+      <app-button variant="secondary" (click)="bulkDeleteConfirmOpen.set(false)">{{ 'mediaLibrary.cancel' | translate }}</app-button>
+      <app-button variant="danger" (click)="proceedBulkDelete()">{{ 'mediaLibrary.confirm' | translate }}</app-button>
+    </div>
+  </app-dialog>
 </section>

src/app/features/backoffice/media/media-library-page.component.ts

@@ -49,6 +49,7 @@ export class MediaLibraryPageComponent implements OnInit {
   @ViewChild('fileInput') private fileInput?: ElementRef<HTMLInputElement>;
 
   protected readonly pendingDelete = signal<MediaAsset | null>(null);
+  protected readonly bulkDeleteConfirmOpen = signal(false);
   protected readonly detailsAsset = signal<MediaAsset | null>(null);
   protected readonly dragActive = signal(false);
   protected readonly totalPages = () => Math.max(1, Math.ceil(this.facade.total() / PAGE_SIZE));
@@ -212,10 +213,15 @@ export class MediaLibraryPageComponent implements OnInit {
     return this.facade.items().filter(a => this.facade.isSelected(a.id));
   }
 
-  protected async bulkDelete(): Promise<void> {
+  protected bulkDelete(): void {
+    if (this.selectedAssets().length === 0) return;
+    this.bulkDeleteConfirmOpen.set(true);
+  }
+
+  protected async proceedBulkDelete(): Promise<void> {
     const ids = this.selectedAssets().map(a => a.id);
+    this.bulkDeleteConfirmOpen.set(false);
     if (ids.length === 0) return;
-    if (!confirm(this.translate.t('mediaLibrary.bulkDeleteConfirm'))) return;
     await this.facade.bulkDelete(ids);
   }