feat(online): session compte, stockage sécurisé et adapter API (ticket #64)

Ajoute l'adapter API distant (infrastructure/remote/auth_api.dart,
http_api_client.dart) et le stockage sécurisé du token d'auth
(infrastructure/security/secure_storage_auth_token_store.dart), câblés
dans app_bootstrap.dart. Étend le modèle Drift (migration
schemaVersion 9→10) et la couche application (ports, use cases,
entités) pour la session de compte. flutter pub get OK (ajout http,
flutter_secure_storage), build_runner OK, dart format appliqué,
analyze propre (mêmes infos préexistantes), 109/109 tests verts,
build APK debug validé. Premier ticket du chantier "Ajouter les
features serveur au client" (#63).

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

lib/infrastructure/security/secure_storage_auth_token_store.dart

@@ -0,0 +1,44 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+import '../../application/application.dart';
+
+final class SecureStorageAuthTokenStore implements AuthTokenStore {
+  const SecureStorageAuthTokenStore({
+    FlutterSecureStorage storage = const FlutterSecureStorage(),
+  }) : _storage = storage;
+
+  static const _tokenKey = 'gametime.auth.token';
+  static const _expiresAtKey = 'gametime.auth.expiresAt';
+
+  final FlutterSecureStorage _storage;
+
+  @override
+  Future<void> saveToken(String token, DateTime expiresAt) async {
+    await _storage.write(key: _tokenKey, value: token);
+    await _storage.write(
+      key: _expiresAtKey,
+      value: expiresAt.toUtc().toIso8601String(),
+    );
+  }
+
+  @override
+  Future<String?> readToken() async {
+    final token = await _storage.read(key: _tokenKey);
+    final expiresAtValue = await _storage.read(key: _expiresAtKey);
+    if (token == null || expiresAtValue == null) {
+      return token;
+    }
+    final expiresAt = DateTime.tryParse(expiresAtValue)?.toUtc();
+    if (expiresAt != null && !expiresAt.isAfter(DateTime.now().toUtc())) {
+      await clearToken();
+      return null;
+    }
+    return token;
+  }
+
+  @override
+  Future<void> clearToken() async {
+    await _storage.delete(key: _tokenKey);
+    await _storage.delete(key: _expiresAtKey);
+  }
+}

lib/infrastructure/security/security.dart

@@ -0,0 +1 @@
+export 'secure_storage_auth_token_store.dart';