fix: user-select style and pre-create iframe in embed.js (#8093)

web/public/embed.js

@@ -73,7 +73,7 @@
         box-shadow: rgba(150, 150, 150, 0.2) 0px 10px 30px 0px, rgba(150, 150, 150, 0.2) 0px 0px 0px 1px;
         bottom: 5rem; right: 1rem; width: 24rem; max-width: calc(100vw - 2rem); height: 40rem;
         max-height: calc(100vh - 6rem); border-radius: 0.75rem; display: flex; z-index: 2147483647;
-        overflow: hidden; left: unset; background-color: #F3F4F6;
+        overflow: hidden; left: unset; background-color: #F3F4F6;user-select: none;
       `;
 
       document.body.appendChild(iframe);
@@ -255,6 +255,9 @@
     if (!document.getElementById(buttonId)) {
       createButton();
     }
+
+    createIframe();
+    document.getElementById(iframeId).style.display = 'none';
   }
 
   // Add esc Exit keyboard event triggered