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>

halkyon_learn_curator/test/kanjivg_test.dart

@@ -1,49 +0,0 @@
-import 'dart:io';
-
-import 'package:halkyon_learn_curator/src/sources/kanjivg.dart';
-import 'package:test/test.dart';
-
-void main() {
-  late Map<String, CharacterStrokes> strokes;
-
-  setUpAll(() async {
-    strokes = kanjivgStrokes(
-      await File('test/fixtures/kanjivg-sample.xml').readAsString(),
-    );
-  });
-
-  test("a character's strokes are its paths in the order they're written", () {
-    final eat = strokes['食']!;
-    expect(eat.strokes, hasLength(9));
-    expect(eat.strokes.first, startsWith('M52.75,10.5c'));
-    expect(eat.strokes.last, startsWith('M51.5,71C'));
-    expect(strokes['あ']!.strokes, hasLength(3));
-  });
-
-  test('its components are the characters KanjiVG first splits it into, '
-      'looking through groups that are none', () {
-    expect(strokes['語']!.components, ['言', '吾']);
-    expect(strokes['食']!.components, isEmpty);
-  });
-
-  test("the character is the code point in the entry's id, not KanjiVG's "
-      'element name, which can be wrong', () {
-    // KanjiVG's U+6A45 (橅) names itself 機.
-    expect(strokes.keys, containsAll(['橅', 'あ', '食', '語']));
-    expect(strokes.keys, isNot(contains('機')));
-  });
-
-  test('the stroke files hold every 256 code points, named by their upper '
-      'bits', () {
-    expect(strokeFileOf('食'), '098');
-    expect(strokeFileOf('あ'), '030');
-    expect(strokeFileOf('𠀋'), '200');
-    final files = strokeFiles(strokes);
-    expect(files.keys, containsAll(['030', '098', '08a', '06a']));
-    expect(files['08a']!['語'], {
-      's': strokes['語']!.strokes,
-      'c': ['言', '吾'],
-    });
-    expect(files['098']!['食'], {'s': strokes['食']!.strokes});
-  });
-}