Add React 19 compatibility shim for Storybook unmountComponentAtNode

Co-authored-by: alichherawalla <[email protected]>

Author: Copilot

.storybook/preview.js

@@ -1,4 +1,19 @@
+import React from 'react';
+import ReactDOM from 'react-dom';
 import enMessages from '../app/translations/en.json';
+
+// React 19 compatibility shim for unmountComponentAtNode
+if (!ReactDOM.unmountComponentAtNode) {
+  ReactDOM.unmountComponentAtNode = (container) => {
+    if (container._reactRootContainer) {
+      container._reactRootContainer.unmount();
+      delete container._reactRootContainer;
+      return true;
+    }
+    return false;
+  };
+}
+
 export const parameters = {
   actions: { argTypesRegex: '^on[A-Z].*' },
   controls: {