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/pinned_statuses/index.js

@@ -8,6 +8,7 @@ import ColumnBackButtonSlim from '../../components/column_back_button_slim';
 import StatusList from '../../components/status_list';
 import { defineMessages, injectIntl } from 'react-intl';
 import ImmutablePureComponent from 'react-immutable-pure-component';
+import { Helmet } from 'react-helmet';
 
 const messages = defineMessages({
   heading: { id: 'column.pins', defaultMessage: 'Pinned post' },
@@ -54,6 +55,9 @@ class PinnedStatuses extends ImmutablePureComponent {
           hasMore={hasMore}
           bindToDocument={!multiColumn}
         />
+        <Helmet>
+          <meta name='robots' content='noindex' />
+        </Helmet>
       </Column>
     );
   }