fix(map): a region is picked on a screen of its own, and a country's map offered once it is picked

The composer showed the map inside its scrolling page, so zooming and
scrolling fought over the wheel. A map question's answer is now a field
that opens the map in the whole window, as a studyset's description is
written, with Save in the app bar; nothing scrolls there, so the wheel
alone zooms. The Prefectures chip stood beside East Asia's countries
before Japan was picked; it now shows once Japan, or a prefecture, is.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -1030,6 +1030,7 @@
   "mapUnknown": "This map needs a newer version of the app.",
   "mapPickRegion": "Choose a part of the map, then tap the region that answers the question. Tiny places have a ring; where rings crowd, zoom in.",
   "mapNonePicked": "No region picked yet",
+  "mapPickTitle": "Pick the region",
   "mapNameJapan": "Japan",
   "mapNameWorld": "World",
   "mapPrefectures": "Prefectures",
@@ -1056,6 +1057,7 @@
   "mapGroupOceania": "Oceania",
   "composerPlaceholderQuestion": "Add question",
   "composerLabelRegion": "Answer",
+  "composerRegionPick": "Tap to pick the region on the map",
 
   "homeStreakTooltip": "Study streak",
   "homeArrange": "Arrange widgets",