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.
