Change public accounts pages to mount the web UI (#19319)

* Change public accounts pages to mount the web UI

* Fix handling of remote usernames in routes

- When logged in, serve web app
- When logged out, redirect to permalink
- Fix `app-body` class not being set sometimes due to name conflict

* Fix missing `multiColumn` prop

* Fix failing test

* Use `discoverable` attribute to control indexing directives

* Fix `<ColumnLoading />` not using `multiColumn`

* Add `noindex` to accounts in REST API

* Change noindex directive to not be rendered by default before a route is mounted

* Add loading indicator for detailed status in web UI

* Fix missing indicator appearing while account is loading in web UI

app/javascript/mastodon/features/favourites/index.js

@@ -11,6 +11,7 @@ import LoadingIndicator from 'mastodon/components/loading_indicator';
 import ScrollableList from 'mastodon/components/scrollable_list';
 import AccountContainer from 'mastodon/containers/account_container';
 import Column from 'mastodon/features/ui/components/column';
+import { Helmet } from 'react-helmet';
 
 const messages = defineMessages({
   refresh: { id: 'refresh', defaultMessage: 'Refresh' },
@@ -80,6 +81,10 @@ class Favourites extends ImmutablePureComponent {
             <AccountContainer key={id} id={id} withNote={false} />,
           )}
         </ScrollableList>
+
+        <Helmet>
+          <meta name='robots' content='noindex' />
+        </Helmet>
       </Column>
     );
   }