feat(online): sync client incrémentale LWW et profil/écrans auth (tickets #65, #67)

Ajoute la synchronisation client incrémentale LWW vers l'API serveur
(application/use_cases.dart: SyncUseCases, ports.dart, migration
Drift schemaVersion 10→11 pour les métadonnées de sync et mappings de
ressources, infrastructure/remote/sync_api.dart) et l'écran de profil
avec entrée sur l'accueil (presentation/profile_screen.dart,
home_screen.dart, presentation.dart). Développés dans le même
worktree partagé par DevBackend et DevFrontend ; commit combiné car
test/presentation/home_screen_test.dart mélange authentiquement les
deux tickets (le test de l'entrée Profil et la mise à jour du fake de
bootstrap requise par le nouveau getter syncUseCases sur
AppDependencies). Corrige au passage une couleur `crimson` inexistante
dans le thème (remplacée par colorScheme.error) et une signature de
paramètres positionnels/nommés incohérente sur un fake de test.
flutter pub get OK, build_runner OK, dart format appliqué, analyze
propre (mêmes infos préexistantes), 119/119 tests verts, build APK
debug validé.

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

lib/application/ports.dart

@@ -73,6 +73,194 @@ abstract interface class RemoteAuthApi {
   Future<void> logout(String token);
 }
 
+enum SyncResourceType {
+  exercise,
+  program,
+  workoutTemplate,
+  workoutHistory,
+  mediaAsset,
+}
+
+enum RemoteSyncPushStatus { accepted, ignoredOlder, error }
+
+enum OnlineSyncStatus { idle, syncing, success, failure }
+
+final class RemoteSyncPushItem {
+  const RemoteSyncPushItem({
+    required this.resourceType,
+    required this.clientId,
+    required this.schemaVersion,
+    required this.clientUpdatedAt,
+    required this.deletedAt,
+    required this.payload,
+  });
+
+  final SyncResourceType resourceType;
+  final String clientId;
+  final int schemaVersion;
+  final DateTime clientUpdatedAt;
+  final DateTime? deletedAt;
+  final Map<String, Object?> payload;
+}
+
+final class RemoteSyncPushItemResult {
+  const RemoteSyncPushItemResult({
+    required this.resourceType,
+    required this.clientId,
+    this.serverId,
+    required this.status,
+    this.serverUpdatedAt,
+    this.errorMessage,
+  });
+
+  final SyncResourceType resourceType;
+  final String clientId;
+  final String? serverId;
+  final RemoteSyncPushStatus status;
+  final DateTime? serverUpdatedAt;
+  final String? errorMessage;
+}
+
+final class RemoteSyncPushResult {
+  const RemoteSyncPushResult({
+    required this.serverCursor,
+    required this.results,
+  });
+
+  final String? serverCursor;
+  final List<RemoteSyncPushItemResult> results;
+}
+
+final class RemoteSyncedItem {
+  const RemoteSyncedItem({
+    required this.resourceType,
+    required this.clientId,
+    required this.serverId,
+    required this.schemaVersion,
+    required this.clientUpdatedAt,
+    required this.serverUpdatedAt,
+    required this.deletedAt,
+    required this.payload,
+  });
+
+  final SyncResourceType resourceType;
+  final String clientId;
+  final String serverId;
+  final int schemaVersion;
+  final DateTime clientUpdatedAt;
+  final DateTime serverUpdatedAt;
+  final DateTime? deletedAt;
+  final Map<String, Object?> payload;
+}
+
+final class RemoteSyncPullResult {
+  const RemoteSyncPullResult({required this.serverCursor, required this.items});
+
+  final String? serverCursor;
+  final List<RemoteSyncedItem> items;
+}
+
+abstract interface class RemoteSyncApi {
+  Future<RemoteSyncPushResult> push({
+    required String deviceId,
+    required List<RemoteSyncPushItem> items,
+    required String token,
+  });
+
+  Future<RemoteSyncPullResult> pull({
+    required String? since,
+    required String token,
+  });
+}
+
+final class SyncMetadataSnapshot {
+  const SyncMetadataSnapshot({
+    this.serverCursor,
+    this.lastSuccessfulSyncAt,
+    this.lastAttemptAt,
+    this.lastFailureAt,
+    this.status = OnlineSyncStatus.idle,
+    this.pendingPushCount,
+  });
+
+  final String? serverCursor;
+  final DateTime? lastSuccessfulSyncAt;
+  final DateTime? lastAttemptAt;
+  final DateTime? lastFailureAt;
+  final OnlineSyncStatus status;
+  final int? pendingPushCount;
+
+  SyncMetadataSnapshot copyWith({
+    Object? serverCursor = _portsUnchanged,
+    Object? lastSuccessfulSyncAt = _portsUnchanged,
+    Object? lastAttemptAt = _portsUnchanged,
+    Object? lastFailureAt = _portsUnchanged,
+    OnlineSyncStatus? status,
+    Object? pendingPushCount = _portsUnchanged,
+  }) {
+    return SyncMetadataSnapshot(
+      serverCursor: serverCursor == _portsUnchanged
+          ? this.serverCursor
+          : serverCursor as String?,
+      lastSuccessfulSyncAt: lastSuccessfulSyncAt == _portsUnchanged
+          ? this.lastSuccessfulSyncAt
+          : lastSuccessfulSyncAt as DateTime?,
+      lastAttemptAt: lastAttemptAt == _portsUnchanged
+          ? this.lastAttemptAt
+          : lastAttemptAt as DateTime?,
+      lastFailureAt: lastFailureAt == _portsUnchanged
+          ? this.lastFailureAt
+          : lastFailureAt as DateTime?,
+      status: status ?? this.status,
+      pendingPushCount: pendingPushCount == _portsUnchanged
+          ? this.pendingPushCount
+          : pendingPushCount as int?,
+    );
+  }
+}
+
+final class RemoteResourceMapping {
+  const RemoteResourceMapping({
+    required this.resourceType,
+    required this.clientId,
+    required this.serverId,
+    required this.serverUpdatedAt,
+  });
+
+  final SyncResourceType resourceType;
+  final String clientId;
+  final String serverId;
+  final DateTime serverUpdatedAt;
+}
+
+final class PendingSyncChange {
+  const PendingSyncChange({required this.changeLogIds, required this.item});
+
+  final List<String> changeLogIds;
+  final RemoteSyncPushItem item;
+}
+
+abstract interface class SyncMetadataRepository {
+  Future<SyncMetadataSnapshot> read();
+  Future<void> save(SyncMetadataSnapshot metadata);
+}
+
+abstract interface class RemoteResourceMappingRepository {
+  Future<RemoteResourceMapping?> find({
+    required SyncResourceType resourceType,
+    required String clientId,
+  });
+  Future<void> save(RemoteResourceMapping mapping);
+}
+
+abstract interface class LocalSyncChangeRepository {
+  Future<List<PendingSyncChange>> listPendingChanges();
+  Future<void> markChangesSynced(List<String> changeLogIds, DateTime syncedAt);
+  Future<bool> applyRemoteItem(RemoteSyncedItem item);
+}
+
+const Object _portsUnchanged = Object();
+
 abstract interface class ExerciseRepository {
   Future<Exercise?> findById(String id);
   Future<List<Exercise>> listActive();
@@ -189,10 +377,16 @@ final class SyncRunSummary {
   const SyncRunSummary({
     required this.pushedChanges,
     required this.pulledChanges,
+    this.skipped = false,
+    this.failed = false,
+    this.message,
   });
 
   final int pushedChanges;
   final int pulledChanges;
+  final bool skipped;
+  final bool failed;
+  final String? message;
 }
 
 abstract interface class SyncGateway {