Fix (beta): correct chat message bg color (#12955)

src-ui/src/app/components/chat/chat/chat.component.html

@@ -8,7 +8,7 @@
       <div class="chat-messages font-monospace small">
         @for (message of messages; track message) {
           <div class="message d-flex flex-row small" [class.justify-content-end]="message.role === 'user'">
-            <div class="p-2 m-2" [class.bg-dark]="message.role === 'user'">
+            <div class="p-2 m-2" [class.bg-body]="message.role === 'user'">
               <span>
                 {{ message.content }}
                 @if (message.isStreaming) { <span class="blinking-cursor">|</span> }