Fix showing new id.ai landing page briefly when visiting legacy domains (#3412)

* Fix showing new id.ai landing page briefly when visiting legacy domains by hiding the SSG page until SvelteKit has mounted.

* Include legacy beta domains.

Author: sea-snake

src/frontend/src/app.html

@@ -34,6 +34,21 @@
     />
     <meta name="twitter:creator" content="@dfinity" />
     <link rel="canonical" href="https://id.ai/" />
+    <style>
+      html[data-temp-hide-ssg="true"] body > div {
+        display: none !important;
+      }
+    </style>
+    <script>
+      // Hide page until it has fully loaded on legacy domains,
+      // this avoids showing the SSG page on these domains.
+      if (
+        window.location.hostname.startsWith("identity.") ||
+        window.location.hostname.startsWith("beta.identity.")
+      ) {
+        document.documentElement.setAttribute("data-temp-hide-ssg", "true");
+      }
+    </script>
     %sveltekit.head%
   </head>
 

src/frontend/src/routes/+layout.svelte

@@ -6,6 +6,9 @@
   const { children } = $props();
 
   onMount(() => {
+    // Show page once it has fully loaded (see app.html)
+    document.documentElement.removeAttribute("data-temp-hide-ssg");
+
     initAnalytics(canisterConfig.analytics_config[0]?.[0]);
     analytics.pageView();
   });