Remove once again email domain from preferred username.

src/lib/components/NavBar.svelte

@@ -203,7 +203,7 @@
 
                     <span class="sr-only ">Open user menu</span>
                     <div class="hidden xl:flex">
-                      {user.preferred_username}
+                      {user.preferred_username.split("@")[0]}
                     </div>
                   </div>
                 </button>
@@ -418,7 +418,7 @@
                   ><path d="M0 0h24v24H0z" fill="none" /><path
                     d="M13 3h-2v10h2V3zm4.83 2.17l-1.42 1.42C17.99 7.86 19 9.81 19 12c0 3.87-3.13 7-7 7s-7-3.13-7-7c0-2.19 1.01-4.14 2.58-5.42L6.17 5.17C4.23 6.82 3 9.26 3 12c0 4.97 4.03 9 9 9s9-4.03 9-9c0-2.74-1.23-5.18-3.17-6.83z"
                   /></svg
-                >Se déconnecter ({user.preferred_username})</a
+                >Se déconnecter ({user.preferred_username.split("@")[0]})</a
               >
             {/if}
           {/if}