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>

test/presentation/home_screen_test.dart

@@ -115,7 +115,14 @@ void main() {
 
 final class _FakeBootstrap implements AppDependencies {
   _FakeBootstrap(_FakeActiveSessionRepository activeRepository)
-    : activeWorkoutSessionUseCases = ActiveWorkoutSessionUseCases(
+    : authUseCases = AuthUseCases(
+        tokenStore: _FakeAuthTokenStore(),
+        accountRepository: _FakeOnlineAccountRepository(),
+        remoteAuthApi: _FakeRemoteAuthApi(),
+        clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
+        ids: _FakeIds(),
+      ),
+      activeWorkoutSessionUseCases = ActiveWorkoutSessionUseCases(
         sessionRepository: activeRepository,
         templateRepository: _FakeWorkoutTemplateRepository(),
         clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
@@ -170,6 +177,9 @@ final class _FakeBootstrap implements AppDependencies {
         clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
       );
 
+  @override
+  final AuthUseCases authUseCases;
+
   @override
   final ExerciseUseCases exerciseUseCases;
 
@@ -249,6 +259,50 @@ final class _FakeIds implements IdGenerator {
   }
 }
 
+final class _FakeAuthTokenStore implements AuthTokenStore {
+  @override
+  Future<void> clearToken() async {}
+
+  @override
+  Future<String?> readToken() async => null;
+
+  @override
+  Future<void> saveToken(String token, DateTime expiresAt) async {}
+}
+
+final class _FakeOnlineAccountRepository implements OnlineAccountRepository {
+  @override
+  Future<void> clearSession() async {}
+
+  @override
+  Future<UserAccountSession?> currentSession() async => null;
+
+  @override
+  Future<void> saveSession(UserAccountSession session) async {}
+}
+
+final class _FakeRemoteAuthApi implements RemoteAuthApi {
+  @override
+  Future<RemoteAuthResult> login({
+    required String email,
+    required String password,
+  }) async {
+    throw const RemoteAuthException(RemoteAuthFailure.network);
+  }
+
+  @override
+  Future<void> logout(String token) async {}
+
+  @override
+  Future<RemoteAuthResult> register({
+    required String email,
+    required String password,
+    String? displayName,
+  }) async {
+    throw const RemoteAuthException(RemoteAuthFailure.network);
+  }
+}
+
 final class _FakeActiveSessionRepository implements ActiveSessionRepository {
   ActiveWorkoutSession? session;
   final restStates = <ActiveRestState>[];