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_flutter/lib/driver.dart

@@ -1,15 +0,0 @@
-// This file is never meant to be used on real apps, just for development.
-// ignore: depend_on_referenced_packages
-import 'package:flutter_driver/driver_extension.dart';
-
-import 'package:halkyon_learn_flutter/main.dart' as app;
-
-void main() {
-  enableFlutterDriverExtension(
-    // Text entry emulation is disabled by default to allow manual usage of the
-    // app, but will be required for agents to type through the app. Set this
-    // parameter to true to switch from manual to automated usage.
-    enableTextEntryEmulation: false,
-  );
-  app.main();
-}