fix(org-site): stabilize landing-page nav auth button

The auth button derived from stores that hydrate in stages, so it
flashed through Login -> Dashboard -> Go to LMS as isLoggedIn and the
role/basePath settled at different times. Gate the label on
appInitApi.isInitializedAndReady so it only renders once the account
(and thus role) has loaded, and show a spinner in the button while a
logged-in user's experience resolves. Add separate loading and disabled
flags to authAction and wire them through all theme navs.

packages/ui/src/custom/org-landing-page/bold/nav.svelte

@@ -10,6 +10,8 @@
     authAction?: {
       label: string;
       href: string;
+      loading?: boolean;
+      disabled?: boolean;
     };
   }
 
@@ -41,7 +43,13 @@
           {/each}
         </nav>
         {#if authAction}
-          <Button href={authAction.href} variant="outline" class="ui:rounded-xl ui:font-bold">
+          <Button
+            href={authAction.href}
+            loading={authAction.loading}
+            disabled={authAction.disabled}
+            variant="outline"
+            class="ui:rounded-xl ui:font-bold"
+          >
             {authAction.label}
           </Button>
         {/if}