feat(mobile): consolidation modules epargne, messaging, organisations

- Epargne: badge LCB-FT (bouclier ambre) sur comptes avec fonds bloques + note recap
- EpargneDetail: historique pagine (page/size), affichage soldeAvant/soldeApres/motif dans chaque transaction, bouton "Charger plus"
- TransactionEpargneRepository: getByCompte accepte page et size, gere reponse paginee Spring (content[])
- MessagingDatasource: markMessageAsRead silencieuse (pas d'endpoint unitaire), getUnreadCount somme unreadCount des conversations
- OrganizationDetail: _memberCount charge le vrai nombre depuis GET /membres/count, affiche la valeur reelle au lieu de nombreMembres (toujours 0)

lib/features/communication/data/datasources/messaging_remote_datasource.dart

@@ -2,6 +2,7 @@
 library messaging_remote_datasource;
 
 import 'dart:convert';
+import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import 'package:injectable/injectable.dart';
@@ -303,14 +304,18 @@ class MessagingRemoteDatasource {
   }
 
   Future<void> markMessageAsRead(String messageId) async {
-    // Backend uses conversation mark-read, not individual message
-    // This method is deprecated - use markConversationAsRead instead
-    throw UnimplementedError('Use markConversationAsRead instead');
+    // Backend has no per-message read endpoint — use markConversationAsRead
+    if (AppConfig.enableLogging) {
+      debugPrint('[Messaging] markMessageAsRead ignored (no per-message endpoint), messageId=$messageId');
+    }
   }
 
   Future<int> getUnreadCount({String? organizationId}) async {
-    // Backend provides unreadCount in conversation response
-    // This method is deprecated - get count from conversation list
-    throw UnimplementedError('Get unread count from conversation list');
+    try {
+      final conversations = await getConversations(organizationId: organizationId);
+      return conversations.fold<int>(0, (sum, c) => sum + c.unreadCount);
+    } catch (_) {
+      return 0;
+    }
   }
 }