Add logged-out access to the web UI (#18961)

app/controllers/home_controller.rb

app/javascript/mastodon/actions/accounts.js

app/javascript/mastodon/actions/markers.js

app/javascript/mastodon/components/logo.js

app/javascript/mastodon/containers/mastodon.js

...javascript/mastodon/features/account/components/header.js

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

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

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

app/javascript/mastodon/features/explore/links.js

app/javascript/mastodon/features/explore/results.js

app/javascript/mastodon/features/explore/suggestions.js

app/javascript/mastodon/features/explore/tags.js

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

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

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

...avascript/mastodon/features/ui/components/columns_area.js

...vascript/mastodon/features/ui/components/compose_panel.js

...ascript/mastodon/features/ui/components/document_title.js

...javascript/mastodon/features/ui/components/link_footer.js