refactor(settings): collapse get_all to aksrt_settings and drop migration UI

Make aksrt_settings the sole theme settings store for get_all(), remove
aksrt_seo_settings/aksrt_basic_settings merge paths, point global.logo
schema at aksrt_settings, and delete the retired settings migration page,
route, REST endpoint, and related SPA surface.

inc/classes/admin/class-aksrt-admin-import-export-controller.php

@@ -71,13 +71,6 @@ class AKSRT_Admin_Import_Export_Controller extends AKSRT_Admin_Controller_Base {
             'permission_callback' => [$this, 'check_permission'],
         ]);
 
-        // Migration status
-        register_rest_route(self::API_NAMESPACE, '/settings/migration-status', [
-            'methods'             => 'GET',
-            'callback'            => [$this, 'rest_migration_status'],
-            'permission_callback' => [$this, 'check_permission'],
-        ]);
-
         // Schema introspection (for frontend to discover available fields)
         register_rest_route(self::API_NAMESPACE, '/settings/schema/(?P<domain>[a-z_]+)', [
             'methods'             => 'GET',
@@ -401,8 +394,4 @@ class AKSRT_Admin_Import_Export_Controller extends AKSRT_Admin_Controller_Base {
 
         return $this->success(['checks' => $checks]);
     }
-
-    /**
-     * Migration status — reports schema version and pending migrations.
-     */
 }