added support for multiple accounts, guardian login bugfixes, ui changes

lib/routing/app_routes.dart

@@ -62,7 +62,9 @@ class AppRoutes {
   /// Root navigator key, set on [MaterialApp]. Lets globally-mounted UI (e.g.
   /// the downloads tray, which lives above the navigator in `MaterialApp.builder`
   /// and is therefore never covered by a pushed route) open full-page routes.
-  static final GlobalKey<NavigatorState> rootNavigatorKey =
+  /// Replaced per account (see `Main`), so a switch starts on a fresh
+  /// navigator.
+  static GlobalKey<NavigatorState> rootNavigatorKey =
       GlobalKey<NavigatorState>();
 
   /// A context that is a descendant of the root navigator (its overlay), safe to