fix: add OpenAPI version field to resolve rendering issue

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/modes/server/api/mod.rs

@@ -12,6 +12,7 @@ use utoipa_swagger_ui::SwaggerUi;
 
 #[derive(OpenApi)]
 #[openapi(
+    openapi = "3.0.0",
     paths(
         status::handle_status,
         item::handle_list_items,