feat: WebSocket temps réel + Finance Workflow + corrections

- Task #6: WebSocket /ws/dashboard + Kafka events (5 topics)
  * Backend: KafkaEventProducer, KafkaEventConsumer
  * Mobile: WebSocketService (reconnection, heartbeat, typed events)
  * DashboardBloc: Auto-refresh depuis WebSocket events

- Finance Workflow: approbations + budgets (backend + mobile)
  * Backend: entities, services, resources, migrations Flyway V6
  * Mobile: features finance_workflow complète avec BLoC

- Corrections DI: interfaces IRepository partout
  * IProfileRepository, IOrganizationRepository, IMembreRepository
  * GetIt configuré avec @injectable

- Spec-Kit: constitution + templates mis à jour
  * .specify/memory/constitution.md enrichie
  * Templates agent, plan, spec, tasks, checklist

- Nettoyage: fichiers temporaires supprimés

Signed-off-by: lions dev Team

unionflow/unionflow-mobile-apps/lib/features/communication/domain/usecases/get_messages.dart

@@ -0,0 +1,31 @@
+/// Use case: Récupérer les messages d'une conversation
+library get_messages;
+
+import 'package:dartz/dartz.dart';
+import 'package:injectable/injectable.dart';
+import '../../../../core/error/failures.dart';
+import '../entities/message.dart';
+import '../repositories/messaging_repository.dart';
+
+@lazySingleton
+class GetMessages {
+  final MessagingRepository repository;
+
+  GetMessages(this.repository);
+
+  Future<Either<Failure, List<Message>>> call({
+    required String conversationId,
+    int? limit,
+    String? beforeMessageId,
+  }) async {
+    if (conversationId.isEmpty) {
+      return Left(ValidationFailure('ID conversation requis'));
+    }
+
+    return await repository.getMessages(
+      conversationId: conversationId,
+      limit: limit,
+      beforeMessageId: beforeMessageId,
+    );
+  }
+}