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

Conflicts:
- `README.md`:
  Upstream updated its README, while we have a completely different one.
  Kept our README.
- `app/controllers/concerns/web_app_controller_concern.rb`:
  Conflict because of glitch-soc's theming system.
  Additionally, glitch-soc has different behavior regarding moved accounts.
  Ported some of the changes, but kept our overall behavior.
- `app/javascript/packs/admin.js`:
  Code changes actually applied to `app/javascript/core/admin.js`

app/javascript/styles/mastodon/admin.scss

@@ -1216,7 +1216,7 @@ a.name-tag,
 
     path:first-child {
       fill: rgba($highlight-text-color, 0.25) !important;
-      fill-opacity: 100% !important;
+      fill-opacity: 1 !important;
     }
 
     path:last-child {