fix: initial hidden state for shadow-box component (#5639)

* Ensure shadow-box starts hidden on initial render.

* add comment to explain not obvious style fix

---------

Co-authored-by: anovazzi1 <otavio2204@gmail.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>

src/frontend/src/pages/FlowPage/components/PageComponent/index.tsx

@@ -630,6 +630,8 @@ export default function Page({ view }: { view?: boolean }): JSX.Element {
               backgroundColor: `${shadowBoxBackgroundColor}`,
               opacity: 0.7,
               pointerEvents: "none",
+              // Prevent shadow-box from showing unexpectedly during initial renders
+              display: "none",
             }}
           ></div>
         </div>