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/core/admin.js

@@ -194,7 +194,7 @@ ready(() => {
   }
 
   document.querySelector('a#add-instance-button')?.addEventListener('click', (e) => {
-    const domain = document.getElementById('by_domain')?.value;
+    const domain = document.querySelector('input[type="text"]#by_domain')?.value;
 
     if (domain) {
       const url = new URL(event.target.href);