Restructure step R: the app is Starsync (dev.foxyz.starsync)

- Linux app id dev.foxyz.starsync, binary starsync; Windows starsync.exe,
  company foxyz; server starsync-server; Dart package starsync; archives
  starsync-<ver>-*.
- 1.2.x compatibility: watch_together and watch-together-server
  launchers (Linux) / copies (Windows) in the archive; the updater
  accepts both names and relaunches the new binary; update.sh/.bat use
  whichever server exists.
- First start copies (never moves) the old support folder and this
  app's Hive boxes out of ~/Documents into <support>/hive; a marker
  makes it run once; AppDirs is a port; settings schema version with
  ordered migrations.
- Launcher entry dev.foxyz.starsync.desktop; the old one removed.
- Repository name and URLs unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/schedule/animeflow.dart

@@ -474,7 +474,7 @@ class AnimeFlowClient {
         _ownsHttp = http == null,
         _delay = delay ?? Future<void>.delayed,
         _now = now ?? DateTime.now,
-        userAgent = userAgent ?? 'watch-together/$appVersion';
+        userAgent = userAgent ?? 'Starsync/$appVersion';
 
   /// Authenticated with the linked Jellyfin account on the same domain
   /// (see [tokenFor]), looked up on every call so a re-link applies.