Fix broken xref targets with page-aliases (#481)

Add page-aliases to resolve xrefs from included ROOT content:
- schema-reg:schema-reg-api.adoc -> manage:schema-reg/schema-reg-api.adoc
- manage:security/authorization/acl.adoc -> security:authorization/acl.adoc

Co-authored-by: Claude Opus 4.5 <[email protected]>

Author: micheleRP

modules/manage/pages/schema-reg/schema-reg-api.adoc

@@ -1,4 +1,5 @@
 = Use the Schema Registry API
+:page-aliases: schema-reg:schema-reg-api.adoc
 :description: Perform common Schema Registry management operations with the API.
 
 include::ROOT:manage:schema-reg/schema-reg-api.adoc[tag=single-source]

modules/security/pages/authorization/acl.adoc

@@ -1,5 +1,5 @@
 = Configure ACLs
-:page-aliases: security:authorization/rbac/acl.adoc
+:page-aliases: security:authorization/rbac/acl.adoc, manage:security/authorization/acl.adoc
 :description: Learn how to use ACLs to configure fine-grained access to Redpanda resources.
 
 include::ROOT:manage:security/authorization/acl.adoc[tag=single-source]