chore: remove legacy models/utils/api/database layers

Also moves stray lib/pages/quel-est-ce-pokemon.code-workspace to repo
root, and fixes two trivial test lint infos (curly_braces_in_flow_
control_structures, constant_identifier_names) to reach clean analyze.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/domain/game_engine_test.dart

@@ -81,7 +81,7 @@ void main() {
     s = _engine.startRound(s, _poke('pikachu'), isShiny: false);
     final o = _engine.submitGuess(s, 'pikachu'); // 5e bonne réponse
     expect(o.state.sessionCorrectCount, 5);
-    expect(o.state.hints, AppConstantsHints + 1);
+    expect(o.state.hints, appConstantsHints + 1);
   });
 
   test('useHint consomme un indice', () {
@@ -121,4 +121,4 @@ void main() {
 }
 
 /// Valeur attendue de hints au démarrage (miroir d'AppConstants.startingHints = 3).
-const AppConstantsHints = 3;
+const appConstantsHints = 3;