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>

.gitea/workflows/ci.yml

@@ -35,9 +35,9 @@ jobs:
       - run: dart test
         working-directory: packages/server
       # Compiling the dedicated server proves it stays Flutter-free.
-      - run: mkdir -p build && dart compile exe bin/server.dart -o build/watch-together-server
+      - run: mkdir -p build && dart compile exe bin/server.dart -o build/starsync-server
         working-directory: packages/server
-      - run: build/watch-together-server --help
+      - run: build/starsync-server --help
         working-directory: packages/server
 
   # The updater's Windows apply path (running exe parked as .old) only