feat: Add supplier exports functionality with scheduling and admin management

includes/class-siti-stock-settings.php

@@ -99,6 +99,7 @@ class Siti_Stock_Settings {
 					'default_status'   => 'instock',
 					'enable_auto_sync' => false,
 					'sync_interval'    => 'hourly',
+					'supplier_exports' => array(),
 				)
 			);
 		}