feat(navbar): add current user balance display in navbar

frontend/src/app/shared/components/navbar/navbar.component.html

@@ -10,7 +10,11 @@
         </div>
       </div>
 
+
       <div class="hidden md:flex items-center space-x-4">
+        <div class="text-white font-bold bg-deep-blue-contrast rounded-full px-4 py-2 text-sm hover:bg-deep-blue-contrast/80 hover:cursor-pointer hover:scale-105 transition-all active:scale-95 select-none duration-300">
+          {{ balance | currency : 'EUR' : 'symbol' : '1.2-2' }}
+        </div>
         @if (!isLoggedIn) {
           <button (click)="login()" class="button-base px-4 py-1.5">Anmelden</button>
         }