feat(todo): the app on halkyon_app, with its own icon

Todo's app is halkyon_app's instance and session gates with Todo's
frame ("Todo" under "Halkyon", its icon, its own sentences) and an
instance check accepting only `todo`; TodoDependencies on an instance,
an empty TodoPerson per person, nothing kept or synced yet. A person
sees an empty home and their account: whose it is on which instance,
switching account, signing out and deleting it (each asking first where
it deletes), and About with the source of what the instance runs and
the licence list. Texts in British English and German. App ID
app.halkyon.todo on every platform, GitHub's callback scheme registered
on Android, no web build.

Its icon is Lucide's list-checks (lucide-static 1.50.0) in the brand's
blues on white: tool/app_icons.py draws its strokes with Pillow and
writes every platform's launcher icon; Lucide's ISC notice joins the
licence list.

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/todo/halkyon_todo_flutter/lib/l10n/app_localizations.dart

@@ -0,0 +1,264 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:intl/intl.dart' as intl;
+
+import 'app_localizations_de.dart';
+import 'app_localizations_en.dart';
+
+// ignore_for_file: type=lint
+
+/// Callers can lookup localized strings with an instance of AppLocalizations
+/// returned by `AppLocalizations.of(context)`.
+///
+/// Applications need to include `AppLocalizations.delegate()` in their app's
+/// `localizationDelegates` list, and the locales they support in the app's
+/// `supportedLocales` list. For example:
+///
+/// ```dart
+/// import 'l10n/app_localizations.dart';
+///
+/// return MaterialApp(
+///   localizationsDelegates: AppLocalizations.localizationsDelegates,
+///   supportedLocales: AppLocalizations.supportedLocales,
+///   home: MyApplicationHome(),
+/// );
+/// ```
+///
+/// ## Update pubspec.yaml
+///
+/// Please make sure to update your pubspec.yaml to include the following
+/// packages:
+///
+/// ```yaml
+/// dependencies:
+///   # Internationalization support.
+///   flutter_localizations:
+///     sdk: flutter
+///   intl: any # Use the pinned version from flutter_localizations
+///
+///   # Rest of dependencies
+/// ```
+///
+/// ## iOS Applications
+///
+/// iOS applications define key application metadata, including supported
+/// locales, in an Info.plist file that is built into the application bundle.
+/// To configure the locales supported by your app, you’ll need to edit this
+/// file.
+///
+/// First, open your project’s ios/Runner.xcworkspace Xcode workspace file.
+/// Then, in the Project Navigator, open the Info.plist file under the Runner
+/// project’s Runner folder.
+///
+/// Next, select the Information Property List item, select Add Item from the
+/// Editor menu, then select Localizations from the pop-up menu.
+///
+/// Select and expand the newly-created Localizations item then, for each
+/// locale your application supports, add a new item and select the locale
+/// you wish to add from the pop-up menu in the Value field. This list should
+/// be consistent with the languages listed in the AppLocalizations.supportedLocales
+/// property.
+abstract class AppLocalizations {
+  AppLocalizations(String locale)
+    : localeName = intl.Intl.canonicalizedLocale(locale.toString());
+
+  final String localeName;
+
+  static AppLocalizations of(BuildContext context) {
+    return Localizations.of<AppLocalizations>(context, AppLocalizations)!;
+  }
+
+  static const LocalizationsDelegate<AppLocalizations> delegate =
+      _AppLocalizationsDelegate();
+
+  /// A list of this localizations delegate along with the default localizations
+  /// delegates.
+  ///
+  /// Returns a list of localizations delegates containing this delegate along with
+  /// GlobalMaterialLocalizations.delegate, GlobalCupertinoLocalizations.delegate,
+  /// and GlobalWidgetsLocalizations.delegate.
+  ///
+  /// Additional delegates can be added by appending to this list in
+  /// MaterialApp. This list does not have to be used at all if a custom list
+  /// of delegates is preferred or required.
+  static const List<LocalizationsDelegate<dynamic>> localizationsDelegates =
+      <LocalizationsDelegate<dynamic>>[
+        delegate,
+        GlobalMaterialLocalizations.delegate,
+        GlobalCupertinoLocalizations.delegate,
+        GlobalWidgetsLocalizations.delegate,
+      ];
+
+  /// A list of this localizations delegate's supported locales.
+  static const List<Locale> supportedLocales = <Locale>[
+    Locale('de'),
+    Locale('en'),
+    Locale('en', 'GB'),
+    Locale('en', 'US'),
+  ];
+
+  /// The app's name: the window's title, and where halkyon_app's texts name the app.
+  ///
+  /// In en, this message translates to:
+  /// **'Halkyon Todo'**
+  String get appTitle;
+
+  /// The app's word in its wordmark, under "Halkyon".
+  ///
+  /// In en, this message translates to:
+  /// **'Todo'**
+  String get launchProduct;
+
+  /// No description provided for @instanceFirstStartSubtitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Choose the instance to keep your tasks on. Someone runs each one; you can add others later.'**
+  String get instanceFirstStartSubtitle;
+
+  /// No description provided for @emailSignInSwitchMessage.
+  ///
+  /// In en, this message translates to:
+  /// **'This address already has an account. The tasks on this device can\'t be combined with it yet: if you switch, they are deleted.'**
+  String get emailSignInSwitchMessage;
+
+  /// Said after a GitHub account nobody on the instance signs in with: the ways in the start screen offers instead.
+  ///
+  /// In en, this message translates to:
+  /// **'Start without an account, or continue with your email address.'**
+  String get startOtherWays;
+
+  /// No description provided for @homeEmptyTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Nothing here yet'**
+  String get homeEmptyTitle;
+
+  /// No description provided for @homeEmptyHint.
+  ///
+  /// In en, this message translates to:
+  /// **'Tasks come with a later version of Halkyon Todo.'**
+  String get homeEmptyHint;
+
+  /// No description provided for @accountTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Account'**
+  String get accountTitle;
+
+  /// No description provided for @accountSignedIn.
+  ///
+  /// In en, this message translates to:
+  /// **'Signed in on {instance}'**
+  String accountSignedIn(String instance);
+
+  /// No description provided for @accountAnonymous.
+  ///
+  /// In en, this message translates to:
+  /// **'Anonymous on {instance}'**
+  String accountAnonymous(String instance);
+
+  /// No description provided for @accountSwitch.
+  ///
+  /// In en, this message translates to:
+  /// **'Switch account'**
+  String get accountSwitch;
+
+  /// No description provided for @accountSignOut.
+  ///
+  /// In en, this message translates to:
+  /// **'Sign out'**
+  String get accountSignOut;
+
+  /// No description provided for @accountSignOutTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Sign out?'**
+  String get accountSignOutTitle;
+
+  /// No description provided for @accountSignOutAnonymousMessage.
+  ///
+  /// In en, this message translates to:
+  /// **'This account can\'t be signed into again, so signing out deletes it.'**
+  String get accountSignOutAnonymousMessage;
+
+  /// No description provided for @accountDelete.
+  ///
+  /// In en, this message translates to:
+  /// **'Delete account'**
+  String get accountDelete;
+
+  /// No description provided for @accountDeleteTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Delete your account?'**
+  String get accountDeleteTitle;
+
+  /// No description provided for @accountDeleteMessage.
+  ///
+  /// In en, this message translates to:
+  /// **'Your account is deleted on the server and on all your devices. This can\'t be undone.'**
+  String get accountDeleteMessage;
+
+  /// No description provided for @aboutTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'About'**
+  String get aboutTitle;
+
+  /// No description provided for @aboutSource.
+  ///
+  /// In en, this message translates to:
+  /// **'The source of what this instance runs:'**
+  String get aboutSource;
+}
+
+class _AppLocalizationsDelegate
+    extends LocalizationsDelegate<AppLocalizations> {
+  const _AppLocalizationsDelegate();
+
+  @override
+  Future<AppLocalizations> load(Locale locale) {
+    return SynchronousFuture<AppLocalizations>(lookupAppLocalizations(locale));
+  }
+
+  @override
+  bool isSupported(Locale locale) =>
+      <String>['de', 'en'].contains(locale.languageCode);
+
+  @override
+  bool shouldReload(_AppLocalizationsDelegate old) => false;
+}
+
+AppLocalizations lookupAppLocalizations(Locale locale) {
+  // Lookup logic when language+country codes are specified.
+  switch (locale.languageCode) {
+    case 'en':
+      {
+        switch (locale.countryCode) {
+          case 'GB':
+            return AppLocalizationsEnGb();
+          case 'US':
+            return AppLocalizationsEnUs();
+        }
+        break;
+      }
+  }
+
+  // Lookup logic when only language code is specified.
+  switch (locale.languageCode) {
+    case 'de':
+      return AppLocalizationsDe();
+    case 'en':
+      return AppLocalizationsEn();
+  }
+
+  throw FlutterError(
+    'AppLocalizations.delegate failed to load unsupported locale "$locale". This is likely '
+    'an issue with the localizations generation tool. Please file an issue '
+    'on GitHub with a reproducible sample app and the gen-l10n configuration '
+    'that was used.',
+  );
+}