docs: add integrations nav, include devtools in index

Author: onmax

docs/content/4.integrations/.navigation.yml

@@ -0,0 +1 @@
+title: Integrations

docs/content/4.integrations/0.index.md

@@ -11,4 +11,7 @@ This module works standalone, but integrates with other tools for enhanced funct
   ::card{title="NuxtHub" icon="i-simple-icons-nuxtdotjs" to="/integrations/nuxthub"}
   Automatic database setup with schema generation and Drizzle ORM.
   ::
+  ::card{title="DevTools" icon="i-simple-icons-nuxtdotjs" to="/integrations/devtools"}
+  Inspect auth config and manage users/sessions during development.
+  ::
 ::