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

Conflicts:
- `app/controllers/settings/preferences_controller.rb`:
  Upstream dropping `digest` from notifications emails while we have more
  notification emails settings.
  Removed `digest` from our list while keeping our extra settings.
- `app/javascript/packs/admin.js`:
  Conflicts caused by glitch-soc's theming system.
  Applied the changes to `app/javascript/core/admin.js`.
- `app/views/settings/preferences/other/show.html.haml`:
  Upstream removed a setting close to a glitch-soc-only setting.
  Applied upstream's change.

app/views/layouts/application.html.haml

@@ -23,6 +23,7 @@
     %link{ rel: 'manifest', href: manifest_path(format: :json) }/
     %meta{ name: 'theme-color', content: '#6364FF' }/
     %meta{ name: 'apple-mobile-web-app-capable', content: 'yes' }/
+    %meta{ name: 'apple-itunes-app', content: 'app-id=1571998974' }/
 
     %title= content_for?(:page_title) ? safe_join([yield(:page_title).chomp.html_safe, title], ' - ') : title