Convert observables to signals.

frontend/src/app/components/publication-list/publication-list.component.html

@@ -1,4 +1,4 @@
-@for(publication of publications$ | async; track publication) {
+@for(publication of publications(); track publication.id) {
     <a [routerLink]="['/publications/' + publication.id]" class="publication">
         <img src="/api/pictures/{{ publication.illustrationId }}"/>
         <div class="body">
@@ -13,4 +13,4 @@
             </span>
         </div>
     </a>
-}
+}