feat: live Gitea changelog, Gitea sidebar link, release title/body extraction

- Admin changelog page now fetches releases live from the public Gitea
  API (https://gitea.kalekber.cc) instead of a baked releases.json file
- Remove /static/releases.json from ui/.gitignore (no longer generated)
- Add Gitea to admin sidebar external tools (admin_nav_gitea i18n key,
  all 5 locales, compiled paraglide JS force-added)
- release.yaml: remove 'Fetch releases from Gitea API' step; extract
  release title and body from the tagged commit message for Gitea releases

ui/.gitignore

@@ -22,5 +22,4 @@ Thumbs.db
 vite.config.js.timestamp-*
 vite.config.ts.timestamp-*
 
-# Generated by CI at build time — do not commit
-/static/releases.json
+