Merge commit '877090518682b6c77ba9bdfa0231afd56daec44d' into glitch-soc/merge-upstream

Conflicts:
- `app/models/concerns/user/has_settings.rb`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `app/views/settings/preferences/appearance/show.html.haml`:
  Not a real conflict, upstream added a setting textually close to a glitch-soc one.
  Added upstream's new setting.
- `config/routes.rb`:
  Upstream moved web app routes to `config/routes/web_app.rb`, while glitch-soc had
  an extra route.
  Moved the extra route to `config/routes/web_app.rb`.
- `spec/controllers/settings/preferences/appearance_controller_spec.rb`:
  This spec got converted to a system spec upstream.
  However, the theme setting works differently in glitch-soc, so the spec had been
  changed.
  Changed the corresponding system spec as well.

.eslintrc.js

@@ -109,7 +109,7 @@ module.exports = defineConfig({
     'react/jsx-equals-spacing': 'error',
     'react/jsx-no-bind': 'error',
     'react/jsx-no-useless-fragment': 'error',
-    'react/jsx-no-target-blank': 'off',
+    'react/jsx-no-target-blank': ['error', { allowReferrer: true }],
     'react/jsx-tag-spacing': 'error',
     'react/jsx-uses-react': 'off', // not needed with new JSX transform
     'react/jsx-wrap-multilines': 'error',