fix(admin): resolve schema builders under AKSRT\Admin\Schema

SchemaProvider still mapped domains to pre-PSR-4 Schema\* strings, so REST
schema loads fatalled with Class Schema\GlobalSchema not found. Point the
builder map at AKSRT\Admin\Schema\* via ::class.

src/AKSRT/Admin/SchemaProvider.php

@@ -251,17 +251,19 @@ class SchemaProvider {
     }
 
     private function get_schema_builder_map(): array {
+        // Builders live under AKSRT\Admin\Schema (Composer PSR-4). Relative
+        // Schema\*::class resolves correctly from this AKSRT\Admin namespace.
         return [
-            'global'       => 'Schema\GlobalSchema',
-            'page_display' => 'Schema\SchemaPageDisplay',
-            'post_list'    => 'Schema\SchemaPostList',
-            'permissions'  => 'Schema\SchemaPermissions',
-            'users'        => 'Schema\SchemaUsers',
-            'payment'      => 'Schema\SchemaPayment',
-            'extensions'   => 'Schema\SchemaExtensions',
-            'tools'        => 'Schema\SchemaTools',
-            'shop'         => 'Schema\SchemaShop',
-            'forum'        => 'Schema\SchemaForum',
+            'global'       => Schema\GlobalSchema::class,
+            'page_display' => Schema\SchemaPageDisplay::class,
+            'post_list'    => Schema\SchemaPostList::class,
+            'permissions'  => Schema\SchemaPermissions::class,
+            'users'        => Schema\SchemaUsers::class,
+            'payment'      => Schema\SchemaPayment::class,
+            'extensions'   => Schema\SchemaExtensions::class,
+            'tools'        => Schema\SchemaTools::class,
+            'shop'         => Schema\SchemaShop::class,
+            'forum'        => Schema\SchemaForum::class,
         ];
     }