Update profile display logic in Step2EnvSetup and modal components for consistency

- Changed profile display from 'realname' to 'username' and 'name' for better clarity and consistency across the application.
- Enhanced CSS for header alignment in multiple views, ensuring a centered layout for improved visual appeal.

frontend/src/views/SimulationView.vue

@@ -317,6 +317,7 @@ onMounted(async () => {
   padding: 0 24px;
   background: #FFF;
   z-index: 100;
+  position: relative;
 }
 
 .brand {
@@ -327,6 +328,12 @@ onMounted(async () => {
   cursor: pointer;
 }
 
+.header-center {
+  position: absolute;
+  left: 50%;
+  transform: translateX(-50%);
+}
+
 .view-switcher {
   display: flex;
   background: #F5F5F5;