fix(onboarding): accept self-hosted addresses

apps/docs/docs/integrations/docker-labels/index.mdx

@@ -52,6 +52,7 @@ services:
 
 Use an address that is reachable where it is needed. A Docker service name can work for server-side integration
 requests, while an app link opened in a browser usually needs a LAN hostname, IP address, or reverse-proxy address.
+Onboarding accepts these self-hosted address formats directly and only requires the field to be non-empty.
 
 ## Homepage label fallback