fix(router): adjust type check for extra parameter in navigation

fix(import): ensure correct typing for passing markdown and imageUrl
fix(recipes): delete local image file on recipe deletion to avoid orphan files

flutter/lib/core/router/app_router.dart

@@ -71,7 +71,9 @@ final appRouterProvider = Provider<GoRouter>((ref) {
           final extra = state.extra;
           String? initialMarkdown;
           String? initialImageUrl;
-          if (extra is Map<String, dynamic>) {
+          // Use 'is Map' without type params — Dart reifies generics, so
+          // Map<String,String?> does NOT match Map<String,dynamic> at runtime.
+          if (extra is Map) {
             initialMarkdown = extra['markdown'] as String?;
             initialImageUrl = extra['imageUrl'] as String?;
           } else if (extra is String) {