Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `app/controllers/home_controller.rb`:
  Upstream made it so `/web` is available to non-logged-in users
  and `/` redirects to `/web` instead of `/about`.
  Kept our version since glitch-soc's WebUI doesn't have what's
  needed yet and I think /about is still a much better landing
  page anyway.
- `app/models/form/admin_settings.rb`:
  Upstream added new settings, and glitch-soc had an extra setting.
  Not really a conflict.
  Added upstream's new settings.
- `app/serializers/initial_state_serializer.rb`:
  Upstream added a new `server` initial state object.
  Not really a conflict.
  Merged upstream's changes.
- `app/views/admin/settings/edit.html.haml`:
  Upstream added new settings.
  Not really a conflict.
  Merged upstream's changes.
- `app/workers/scheduler/feed_cleanup_scheduler.rb`:
  Upstream refactored that part and removed the file.
  Ported our relevant changes into `app/lib/vacuum/feeds_vacuum.rb`
- `config/settings.yml`:
  Upstream added new settings.
  Not a real conflict.
  Added upstream's new settings.

app/serializers/initial_state_serializer.rb

@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
 class InitialStateSerializer < ActiveModel::Serializer
+  include RoutingHelper
+
   attributes :meta, :compose, :accounts,
              :media_attachments, :settings,
              :max_toot_chars, :poll_limits,
-             :languages
+             :languages, :server
 
   has_one :push_subscription, serializer: REST::WebPushSubscriptionSerializer
   has_one :role, serializer: REST::RoleSerializer
@@ -38,6 +40,7 @@ class InitialStateSerializer < ActiveModel::Serializer
       mascot: instance_presenter.mascot&.file&.url,
       profile_directory: Setting.profile_directory,
       trends: Setting.trends,
+      registrations_open: Setting.registrations_mode != 'none' && !Rails.configuration.x.single_user_mode,
     }
 
     if object.current_account
@@ -99,6 +102,13 @@ class InitialStateSerializer < ActiveModel::Serializer
     LanguagesHelper::SUPPORTED_LOCALES.map { |(key, value)| [key, value[0], value[1]] }
   end
 
+  def server
+    {
+      hero: instance_presenter.hero&.file&.url || instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'),
+      description: instance_presenter.site_short_description.presence || I18n.t('about.about_mastodon_html'),
+    }
+  end
+
   private
 
   def instance_presenter