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/infrastructure/remote/sync_api.dart

@@ -0,0 +1,171 @@
+import '../../application/application.dart';
+import 'http_api_client.dart';
+
+final class HttpRemoteSyncApi implements RemoteSyncApi {
+  const HttpRemoteSyncApi(this.client);
+
+  final HttpApiClient client;
+
+  @override
+  Future<RemoteSyncPushResult> push({
+    required String deviceId,
+    required List<RemoteSyncPushItem> items,
+    required String token,
+  }) async {
+    final response = await client.postJson(
+      '/sync/push',
+      bearerToken: token,
+      body: {
+        'deviceId': deviceId,
+        'items': items.map(_pushItemToJson).toList(),
+      },
+    );
+    return RemoteSyncPushResult(
+      serverCursor: _optionalString(response, 'serverCursor'),
+      results: (_list(
+        response,
+        'results',
+      )).map((item) => _pushItemResultFromJson(_map(item))).toList(),
+    );
+  }
+
+  @override
+  Future<RemoteSyncPullResult> pull({
+    required String? since,
+    required String token,
+  }) async {
+    final response = await client.getJson(
+      '/sync/pull',
+      bearerToken: token,
+      queryParameters: {'since': since},
+    );
+    return RemoteSyncPullResult(
+      serverCursor: _optionalString(response, 'serverCursor'),
+      items: (_list(
+        response,
+        'items',
+      )).map((item) => _syncedItemFromJson(_map(item))).toList(),
+    );
+  }
+
+  Map<String, Object?> _pushItemToJson(RemoteSyncPushItem item) => {
+    'resourceType': _resourceTypeToWire(item.resourceType),
+    'clientId': item.clientId,
+    'schemaVersion': item.schemaVersion,
+    'clientUpdatedAt': item.clientUpdatedAt.toUtc().toIso8601String(),
+    'deletedAt': item.deletedAt?.toUtc().toIso8601String(),
+    'payload': item.payload,
+  };
+
+  RemoteSyncPushItemResult _pushItemResultFromJson(Map<String, Object?> json) {
+    return RemoteSyncPushItemResult(
+      resourceType: _resourceTypeFromWire(
+        _requiredString(json, 'resourceType'),
+      ),
+      clientId: _requiredString(json, 'clientId'),
+      serverId: _optionalString(json, 'serverId'),
+      status: _pushStatusFromWire(_requiredString(json, 'status')),
+      serverUpdatedAt: _optionalDateTime(json, 'serverUpdatedAt'),
+      errorMessage: _optionalString(json, 'message'),
+    );
+  }
+
+  RemoteSyncedItem _syncedItemFromJson(Map<String, Object?> json) {
+    return RemoteSyncedItem(
+      resourceType: _resourceTypeFromWire(
+        _requiredString(json, 'resourceType'),
+      ),
+      clientId: _requiredString(json, 'clientId'),
+      serverId: _requiredString(json, 'serverId'),
+      schemaVersion: _requiredInt(json, 'schemaVersion'),
+      clientUpdatedAt: _requiredDateTime(json, 'clientUpdatedAt'),
+      serverUpdatedAt: _requiredDateTime(json, 'serverUpdatedAt'),
+      deletedAt: _optionalDateTime(json, 'deletedAt'),
+      payload: _map(json['payload']),
+    );
+  }
+}
+
+String _resourceTypeToWire(SyncResourceType type) => switch (type) {
+  SyncResourceType.exercise => 'exercise',
+  SyncResourceType.program => 'program',
+  SyncResourceType.workoutTemplate => 'workoutTemplate',
+  SyncResourceType.workoutHistory => 'workoutHistory',
+  SyncResourceType.mediaAsset => 'mediaAsset',
+};
+
+SyncResourceType _resourceTypeFromWire(String value) => switch (value) {
+  'exercise' => SyncResourceType.exercise,
+  'program' => SyncResourceType.program,
+  'workoutTemplate' => SyncResourceType.workoutTemplate,
+  'workoutHistory' => SyncResourceType.workoutHistory,
+  'mediaAsset' => SyncResourceType.mediaAsset,
+  _ => throw RemoteAuthException(
+    RemoteAuthFailure.unknown,
+    'Unknown sync resource type: $value',
+  ),
+};
+
+RemoteSyncPushStatus _pushStatusFromWire(String value) => switch (value) {
+  'accepted' => RemoteSyncPushStatus.accepted,
+  'ignoredOlder' => RemoteSyncPushStatus.ignoredOlder,
+  'error' => RemoteSyncPushStatus.error,
+  _ => throw RemoteAuthException(
+    RemoteAuthFailure.unknown,
+    'Unknown sync push status: $value',
+  ),
+};
+
+List<Object?> _list(Map<String, Object?> json, String key) {
+  final value = json[key];
+  if (value is List) {
+    return value.cast<Object?>();
+  }
+  return const [];
+}
+
+Map<String, Object?> _map(Object? value) {
+  if (value is Map) {
+    return Map<String, Object?>.from(value);
+  }
+  throw const RemoteAuthException(
+    RemoteAuthFailure.unknown,
+    'Expected JSON object.',
+  );
+}
+
+String _requiredString(Map<String, Object?> json, String key) {
+  final value = json[key];
+  if (value is String && value.trim().isNotEmpty) {
+    return value;
+  }
+  throw RemoteAuthException(
+    RemoteAuthFailure.unknown,
+    '$key is missing from sync response.',
+  );
+}
+
+String? _optionalString(Map<String, Object?> json, String key) {
+  final value = json[key];
+  return value is String && value.trim().isNotEmpty ? value : null;
+}
+
+int _requiredInt(Map<String, Object?> json, String key) {
+  final value = json[key];
+  if (value is int) {
+    return value;
+  }
+  throw RemoteAuthException(
+    RemoteAuthFailure.unknown,
+    '$key is missing from sync response.',
+  );
+}
+
+DateTime _requiredDateTime(Map<String, Object?> json, String key) {
+  return DateTime.parse(_requiredString(json, key)).toUtc();
+}
+
+DateTime? _optionalDateTime(Map<String, Object?> json, String key) {
+  final value = _optionalString(json, key);
+  return value == null ? null : DateTime.parse(value).toUtc();
+}