Fix: prevent sidebar animation at startup (#12615)

src-ui/src/app/components/app-frame/app-frame.component.scss

@@ -94,12 +94,18 @@ main {
   }
 
   .sidebar.slim:not(.animating) {
+    transition: none;
+
     li.nav-item span,
     .sidebar-heading span {
       display: none;
     }
   }
 
+  .sidebar.slim:not(.animating) ~ main.col-slim {
+    transition: none;
+  }
+
   .sidebar.animating {
     li.nav-item span,
     .sidebar-heading span {