feat: live Runware model sync with 24h cache and Sync Now button (v0.15.0)

Replace hardcoded model registry with live-sync system.

New PRAutoBlogger_Runware_Model_Catalog class fetches the Runware model
catalog daily, caches in WP options (24h TTL), and falls back to the
hardcoded 15-model list if the API is unavailable. Sync Now button
in PRAdmin for on-demand refresh. Eliminates the drift that caused
silent model fallback bugs (v0.13.8, v0.14.0).

includes/admin/class-settings-fields-extended.php

@@ -259,5 +259,13 @@ class PRAutoBlogger_Settings_Fields_Extended {
 				'description' => __( 'When the provider rejects an image prompt as NSFW, retry once with a generic fallback scene built from the article title. Disable to fail fast if the filter gets trigger-happy.', 'prautoblogger' ),
 			),
 		);
+			array(
+				'id'          => 'prautoblogger_runware_model_catalog',
+				'label'       => __( 'Runware Model Catalog', 'prautoblogger' ),
+				'type'        => 'runware_catalog_sync',
+				'section'     => 'prautoblogger_images',
+				'description' => __( 'Live model catalog sync status and on-demand refresh.', 'prautoblogger' ),
+			),
+			);
 	}
 }