refactor(halkyon_app): the account section, About, the language and countries' names, shared

What Learn and Todo each held now comes from halkyon_app:
- AccountTiles: whose account on which instance, switching, signing
  out (asking first for an anonymous account, as it deletes it) and
  deleting it (asking first), the app's own words passed in.
- showAppAbout: the app's name, version, icon and legalese as it gives
  them, the source of what the instance runs (AppDependencies gains
  sourceCodeUrl), the app's own parts, the licence list.
- resolveAppLocale: the first preferred language the app speaks, never
  by country alone, British English otherwise.
- AssetCountryNames, the default of InstanceGate and InstanceScope:
  Unicode CLDR 48.2's territory names in English and German
  (tool/country_names.py, 7.6 KB), Hong Kong, Macao, Myanmar and
  Palestine by their short names as Learn's world map has them, so
  Todo says "Germany (EU)" where it said "DE (EU)".

Learn's texts read as before in every language; its About bloc and
gateway, its country names from the world map and the keys only the
moved code used are gone, as are Todo's copies.

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

packages/halkyon_app/lib/l10n/halkyon_app_de.arb

@@ -28,6 +28,15 @@
   "accountRemoveTitle": "Konto entfernen?",
   "accountRemoveMessage": "Entfernt das Konto auf {name} von diesem Gerät, mit allem, was das Gerät davon hat. Was es synchronisiert hat, bleibt auf {name}: Melde dich dort wieder an, um es wiederzuhaben. In ein anonymes Konto kann man sich nicht wieder anmelden.",
   "accountRemoveConfirm": "Entfernen",
+  "accountSignedInOn": "Angemeldet auf {instance}",
+  "accountAnonymousOn": "Anonym auf {instance}",
+  "accountSwitch": "Konto wechseln",
+  "accountSignOut": "Abmelden",
+  "accountSignOutTitle": "Abmelden?",
+  "accountDelete": "Konto löschen",
+  "accountDeleteTitle": "Dein Konto löschen?",
+  "aboutSourceCode": "Der Quellcode dessen, was diese Instanz ausführt:",
+  "aboutSourceUnreachable": "Diese Instanz war nicht erreichbar, um nach ihrem Quellcode zu fragen.",
   "sessionUnreachable": "Der Server war nicht erreichbar.",
   "personDataFailed": "Die Daten dieses Geräts konnten nicht geöffnet werden.",
   "startSignedOut": "Abgemeldet",

packages/halkyon_app/lib/l10n/halkyon_app_en.arb

@@ -107,6 +107,29 @@
     }
   },
   "accountRemoveConfirm": "Remove",
+  "accountSignedInOn": "Signed in on {instance}",
+  "@accountSignedInOn": {
+    "placeholders": {
+      "instance": {
+        "type": "String"
+      }
+    }
+  },
+  "accountAnonymousOn": "Anonymous on {instance}",
+  "@accountAnonymousOn": {
+    "placeholders": {
+      "instance": {
+        "type": "String"
+      }
+    }
+  },
+  "accountSwitch": "Switch account",
+  "accountSignOut": "Sign out",
+  "accountSignOutTitle": "Sign out?",
+  "accountDelete": "Delete account",
+  "accountDeleteTitle": "Delete your account?",
+  "aboutSourceCode": "The source of what this instance runs:",
+  "aboutSourceUnreachable": "Couldn't reach this instance to ask where its source is.",
   "sessionUnreachable": "Couldn't reach the server.",
   "personDataFailed": "Couldn't open this device's data.",
   "startSignedOut": "Signed out",

packages/halkyon_app/lib/l10n/halkyon_app_localizations.dart

@@ -271,6 +271,60 @@ abstract class HalkyonAppLocalizations {
   /// **'Remove'**
   String get accountRemoveConfirm;
 
+  /// No description provided for @accountSignedInOn.
+  ///
+  /// In en, this message translates to:
+  /// **'Signed in on {instance}'**
+  String accountSignedInOn(String instance);
+
+  /// No description provided for @accountAnonymousOn.
+  ///
+  /// In en, this message translates to:
+  /// **'Anonymous on {instance}'**
+  String accountAnonymousOn(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 @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 @aboutSourceCode.
+  ///
+  /// In en, this message translates to:
+  /// **'The source of what this instance runs:'**
+  String get aboutSourceCode;
+
+  /// No description provided for @aboutSourceUnreachable.
+  ///
+  /// In en, this message translates to:
+  /// **'Couldn\'t reach this instance to ask where its source is.'**
+  String get aboutSourceUnreachable;
+
   /// No description provided for @sessionUnreachable.
   ///
   /// In en, this message translates to:

packages/halkyon_app/lib/l10n/halkyon_app_localizations_de.dart

@@ -114,6 +114,39 @@ class HalkyonAppLocalizationsDe extends HalkyonAppLocalizations {
   @override
   String get accountRemoveConfirm => 'Entfernen';
 
+  @override
+  String accountSignedInOn(String instance) {
+    return 'Angemeldet auf $instance';
+  }
+
+  @override
+  String accountAnonymousOn(String instance) {
+    return 'Anonym auf $instance';
+  }
+
+  @override
+  String get accountSwitch => 'Konto wechseln';
+
+  @override
+  String get accountSignOut => 'Abmelden';
+
+  @override
+  String get accountSignOutTitle => 'Abmelden?';
+
+  @override
+  String get accountDelete => 'Konto löschen';
+
+  @override
+  String get accountDeleteTitle => 'Dein Konto löschen?';
+
+  @override
+  String get aboutSourceCode =>
+      'Der Quellcode dessen, was diese Instanz ausführt:';
+
+  @override
+  String get aboutSourceUnreachable =>
+      'Diese Instanz war nicht erreichbar, um nach ihrem Quellcode zu fragen.';
+
   @override
   String get sessionUnreachable => 'Der Server war nicht erreichbar.';
 

packages/halkyon_app/lib/l10n/halkyon_app_localizations_en.dart

@@ -114,6 +114,38 @@ class HalkyonAppLocalizationsEn extends HalkyonAppLocalizations {
   @override
   String get accountRemoveConfirm => 'Remove';
 
+  @override
+  String accountSignedInOn(String instance) {
+    return 'Signed in on $instance';
+  }
+
+  @override
+  String accountAnonymousOn(String instance) {
+    return 'Anonymous on $instance';
+  }
+
+  @override
+  String get accountSwitch => 'Switch account';
+
+  @override
+  String get accountSignOut => 'Sign out';
+
+  @override
+  String get accountSignOutTitle => 'Sign out?';
+
+  @override
+  String get accountDelete => 'Delete account';
+
+  @override
+  String get accountDeleteTitle => 'Delete your account?';
+
+  @override
+  String get aboutSourceCode => 'The source of what this instance runs:';
+
+  @override
+  String get aboutSourceUnreachable =>
+      'Couldn\'t reach this instance to ask where its source is.';
+
   @override
   String get sessionUnreachable => 'Couldn\'t reach the server.';