cleanup: defaultProps -> JS default params on our function components

React 19 drops defaultProps on function components. Converted the 9 of
ours that used it (App, Navigation, ReSendEmail, Reconnect, OAuthLoginButton,
PageHeader, Page, EditDocument, EditSubscription) to destructured default
params; App defaults userId/emailAddress in its withTracker instead (it
spreads {...props} widely). Class components keep defaultProps (still
supported). The only defaultProps warnings left are from the react-share
npm package (CreatedButton/Icon), not our code. REST smoke byte-identical.

imports/ui/pages/EditSubscription/EditSubscription.js

@@ -6,17 +6,13 @@ import Subscriptions from '../../../api/Subscriptions/Subscriptions';
 import SubscriptionEditor from '../../components/SubscriptionEditor/SubscriptionEditor';
 import NotFound from '../NotFound/NotFound';
 
-const EditSubscription = ({ doc, history }) => (doc ? (
+const EditSubscription = ({ doc = null, history }) => (doc ? (
   <div className="EditSubscription">
     <h4 className="page-header">{`Editing "${doc.title}"`}</h4>
     <SubscriptionEditor doc={doc} history={history} />
   </div>
 ) : <NotFound />);
 
-EditSubscription.defaultProps = {
-  doc: null
-};
-
 EditSubscription.propTypes = {
   doc: PropTypes.object,
   history: PropTypes.object.isRequired