halkyon_app: data locations as precise as a country or a state

An operator's DATA_LOCATION and BACKUP_LOCATION may name a subdivision
(ISO 3166-2, US-CA, DE-BY) besides the EU or a country. The app adds
"(EU)" to a member country and the country to a subdivision ("Germany
(EU)", "California, United States", "Bavaria, Germany (EU)"), in
English and German, and shows the most specific flag there is: a
subdivision's own where the flag package has one, else its country's.
Subdivision names come from Unicode CLDR 48.2 (tool/subdivision_names.py),
bundled with their licence, which the app registers.

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/test/instance/cldr_license_test.dart

@@ -0,0 +1,26 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_app/halkyon_app.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  test("Unicode CLDR's notice joins the licence list with the flags', as "
+      'their licences ask', () async {
+    registerHalkyonAppLicenses();
+
+    final notices = {
+      await for (final entry in LicenseRegistry.licenses)
+        for (final package in entry.packages)
+          package: entry.paragraphs
+              .map((paragraph) => paragraph.text)
+              .join('\n'),
+    };
+    expect(notices['Unicode CLDR'], contains('UNICODE LICENSE V3'));
+    expect(notices['Unicode CLDR'], contains('Unicode, Inc.'));
+    expect(
+      notices['flag-icons'],
+      contains('Copyright (c) 2013 Panayiotis Lipiridis'),
+    );
+  });
+}