fix(perf): lazy load super admin dashboard stats (#15147)

The super admin landing page runs all its stat queries synchronously
before rendering anything. On large installs the exact `COUNT(*)` on
conversations and the 30-day chart group-by scan the whole table and
exceed the request timeout, so the first page load fails and the console
is unreachable.

tailwind.config.js

@@ -23,6 +23,7 @@ const tailwindConfig = {
   darkMode: 'class',
   content: [
     './enterprise/app/views/**/*.erb',
+    './app/javascript/superadmin_pages/**/*.vue',
     './app/javascript/widget/**/*.vue',
     './app/javascript/v3/**/*.vue',
     './app/javascript/dashboard/**/*.vue',