chore: Halkyon Learn moves into apps/learn

Its server, client, app and curator, and the tools that write its
assets (maps, Anki fixtures, icons), as they are; paths are fixed in
the commits that follow.

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/learn/halkyon_learn_server/test/integration/instance/instance_test.dart

@@ -0,0 +1,59 @@
+import 'package:halkyon_learn_server/src/auth/learn_base.dart';
+import 'package:halkyon_learn_server/src/instance/app_compatibility.dart';
+import 'package:test/test.dart';
+
+import '../support/auth_fixtures.dart';
+import '../test_tools/serverpod_test_tools.dart';
+
+void main() {
+  withServerpod('What the instance offers', (sessionBuilder, endpoints) {
+    setUp(() => useLearnBase(sessionBuilder));
+
+    test('names this repository as the source when the operator set '
+        'nothing', () async {
+      // The tests run without SOURCE_URL.
+      final info = await endpoints.instance.info(
+        sessionBuilder.copyWith(
+          authentication: AuthenticationOverride.unauthenticated(),
+        ),
+      );
+
+      expect(info.sourceCodeUrl, upstreamSourceCodeUrl);
+    });
+
+    test('names the oldest app build it still works with, to anyone, so an '
+        'older app can say it needs an update', () async {
+      final info = await endpoints.instance.info(
+        sessionBuilder.copyWith(
+          authentication: AuthenticationOverride.unauthenticated(),
+        ),
+      );
+
+      expect(info.minimumAppBuild, minimumAppBuild);
+    });
+
+    test('suggests no Jellyfin server where the operator set none and the '
+        'instance has no domain of its own (localhost)', () async {
+      final info = await endpoints.instance.info(
+        sessionBuilder.copyWith(
+          authentication: AuthenticationOverride.unauthenticated(),
+        ),
+      );
+
+      expect(info.jellyfinUrl, isNull);
+    });
+
+    test('says nothing of where its data and backups are where the '
+        'operator said nothing', () async {
+      // The tests run without DATA_LOCATION and BACKUP_LOCATION.
+      final info = await endpoints.instance.info(
+        sessionBuilder.copyWith(
+          authentication: AuthenticationOverride.unauthenticated(),
+        ),
+      );
+
+      expect(info.dataLocation, isNull);
+      expect(info.backupLocation, isNull);
+    });
+  });
+}