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/test/settings_schema_test.dart

@@ -0,0 +1,57 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:hive_ce/hive.dart';
+import 'package:starsync/src/state/settings_schema.dart';
+
+void main() {
+  group('settings schema', () {
+    late Directory dir;
+    setUp(() async {
+      dir = await Directory.systemTemp.createTemp('starsync-schema');
+      Hive.init(dir.path);
+    });
+    tearDown(() async {
+      await Hive.close();
+      await dir.delete(recursive: true);
+    });
+
+    test('a box without a version is at 1 and gets stamped', () async {
+      final box = await Hive.openBox('settings');
+      expect(await migrateSettings(box), isEmpty);
+      expect(box.get(settingsSchemaKey), settingsSchemaVersion);
+    });
+
+    test('steps run in order, only past the stored version', () async {
+      final box = await Hive.openBox('settings');
+      await box.put(settingsSchemaKey, 1);
+      await box.put('old', 'x');
+      final order = <int>[];
+      final steps = [
+        SettingsMigration(3, 'c', (b) async {
+          order.add(3);
+          await b.put('c', b.get('new'));
+        }),
+        SettingsMigration(2, 'rename old to new', (b) async {
+          order.add(2);
+          await b.put('new', b.get('old'));
+          await b.delete('old');
+        }),
+        SettingsMigration(4, 'not yet', (b) async => order.add(4)),
+      ];
+      final ran = await migrateSettings(box, steps: steps, current: 3);
+      expect(order, [2, 3]);
+      expect(ran, ['settings schema 2: rename old to new', 'settings schema 3: c']);
+      expect(box.get('c'), 'x');
+      expect(box.get(settingsSchemaKey), 3);
+      expect(await migrateSettings(box, steps: steps, current: 3), isEmpty);
+    });
+
+    test('a box from a newer build is left as it is', () async {
+      final box = await Hive.openBox('settings');
+      await box.put(settingsSchemaKey, 9);
+      expect(await migrateSettings(box), hasLength(1));
+      expect(box.get(settingsSchemaKey), 9);
+    });
+  });
+}