feat(train): Settings choose the app's appearance and language

The developer asked for Train to offer what Learn's Settings offer first
(ADR 0014's amendment of 4 Nov 2026). Train passed a fixed look, the
system's theme and language; it now opens halkyon_app's LookCubit on
<app support>/look.json in main, provides it above InstanceGate, and its
start screens and each person's MaterialApp follow it. Settings show
DeviceLookCard right after the Sync and operator's cards, as Learn's,
offering English (UK), English (US) and Deutsch (trainLanguages).

The app's tests tapping Delete account and About now scroll them into
view first (tapInSettings, as Todo's and Meditate's): the card moved
them below the phone's fold.

Whats-New: Settings: choose the app's appearance and language.
Whats-New-De: Einstellungen: Darstellung und Sprache der App wählen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/lib/main.dart

@@ -32,6 +32,11 @@ Future<void> main() async {
     sharesStorage: device.storage.sharesWith,
   );
   await instances.load(usedBefore: device.storage.usedBefore());
+  // The device's appearance and language, read before the first frame so
+  // that it opens in them.
+  final look = await LookCubit.open(
+    FileLookStore(File(p.join(device.support, 'look.json'))),
+  );
   runApp(
     WhatsNewScope(
       whatsNew: WhatsNew(
@@ -47,6 +52,7 @@ Future<void> main() async {
         // answers too, but holds nothing of this app's.
         checker: ServerpodInstanceChecker(app: 'train'),
         open: (instance) => TrainDependencies.create(instance, device),
+        look: look,
       ),
     ),
   );