feat(app): map questions on Japan's prefectures

A map question is a multiple-choice card drawn on a map: the composer's
Map kind takes the region tapped as its answer, and studying it means
tapping a region and checking, the right one green and a wrong pick red,
each named. The map of Japan's 47 prefectures comes from Natural Earth
(public domain), built by tool/maps/japan_prefectures.py from release
v5.1.2 (its download checked by hash): simplified, small islands
dropped, rounded; about 107 KB. Maps are drawn to fit, tappable and
zoomable for small regions.

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/l10n/app_localizations_en.dart

@@ -958,6 +958,22 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get studysetResetDone => 'Progress reset';
 
+  @override
+  String get mapUnknown => 'This map needs a newer version of the app.';
+
+  @override
+  String get mapPickRegion =>
+      'Tap the region that answers the question; pinch or scroll to zoom.';
+
+  @override
+  String get mapNonePicked => 'No region picked yet';
+
+  @override
+  String get composerPlaceholderQuestion => 'Add question';
+
+  @override
+  String get composerLabelRegion => 'Answer';
+
   @override
   String get commonCancel => 'Cancel';