Set chat body height to remove UX jitter on chat history load in Web, Desktop

src/interface/desktop/chat.html

@@ -1196,6 +1196,7 @@
 
 
         #chat-body {
+            height: 100%;
             font-size: small;
             margin: 0px;
             line-height: 20px;

src/khoj/interface/web/chat.html

@@ -1263,6 +1263,7 @@ To get started, just start typing below. You can also type / to see a list of co
         }
 
         #chat-body {
+            height: 100%;
             font-size: medium;
             margin: 0px;
             line-height: 20px;