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/state/settings.dart

@@ -6,6 +6,7 @@ import 'package:signals/signals_flutter.dart';
 
 import '../controls/model/controls_prefs.dart';
 import '../shaders/shader_presets.dart';
+import 'settings_schema.dart';
 
 // App preferences (Settings page), one Hive box. Signals start at their
 // defaults and take the stored values once [AppSettings.ensureLoaded]
@@ -134,6 +135,9 @@ class AppSettings {
   Future<void> _loadNow() async {
     try {
       final box = _box = await Hive.openBox(settingsBoxName);
+      for (final line in await migrateSettings(box)) {
+        debugPrint(line);
+      }
       final mode = box.get(_keyHwdecMode);
       hwdecMode.value = HwdecMode.values
               .where((m) => m.name == mode)

apps/desktop/lib/src/state/settings_schema.dart

@@ -0,0 +1,46 @@
+import 'package:hive_ce/hive.dart';
+
+// The `settings` box's layout version and the ordered steps between
+// versions. A step rewrites stored values for a new layout (renamed keys,
+// changed formats); the restructure steps add theirs here.
+
+/// The layout this build reads. 1: the layout of 1.2.x, where versioning
+/// starts (a box without a version is at 1).
+const settingsSchemaVersion = 1;
+
+/// The box key holding the stored version.
+const settingsSchemaKey = 'schemaVersion';
+
+/// One step: brings a box at `to - 1` to [to].
+class SettingsMigration {
+  final int to;
+  /// For the log ("settings schema 2: ...").
+  final String what;
+  final Future<void> Function(Box box) apply;
+  const SettingsMigration(this.to, this.what, this.apply);
+}
+
+/// Every step in order of [SettingsMigration.to] (2, 3, ...); empty while
+/// version 1 is current.
+const settingsMigrations = <SettingsMigration>[];
+
+/// Runs the [steps] past the box's stored version up to [current], in
+/// order, storing the version after each, then stores [current]. A box
+/// from a newer build (a downgrade) is left as it is. Returns a log line
+/// per step run.
+Future<List<String>> migrateSettings(Box box,
+    {List<SettingsMigration> steps = settingsMigrations, int current = settingsSchemaVersion}) async {
+  final stored = box.get(settingsSchemaKey);
+  var at = stored is int ? stored : 1;
+  if (at > current) return ['settings schema $at is newer than this build ($current): left as is'];
+  final ran = <String>[];
+  for (final step in [...steps]..sort((a, b) => a.to.compareTo(b.to))) {
+    if (step.to <= at || step.to > current) continue;
+    await step.apply(box);
+    at = step.to;
+    await box.put(settingsSchemaKey, at);
+    ran.add('settings schema ${step.to}: ${step.what}');
+  }
+  if (stored != current) await box.put(settingsSchemaKey, current);
+  return ran;
+}