feat: add monthly settlement read model

Implements REQ-022 monthly settlement read-model foundation.

jarca_ledger_mcp/application/__init__.py

@@ -9,6 +9,7 @@ from . import categorization_services as _categorization_services
 from . import cross_transfer_service as _cross_transfer_service
 from . import imports_service as _imports_service
 from . import import_transfer_services as _import_transfer_services
+from . import monthly_settlement_service as _monthly_settlement_service
 from . import reconciliation_service as _reconciliation_service
 from . import shared as shared
 from . import system_services as _system_services
@@ -27,6 +28,7 @@ _EXPORT_MODULES = (
     _cross_transfer_service,
     _imports_service,
     _import_transfer_services,
+    _monthly_settlement_service,
     _reconciliation_service,
     _system_services,
     _transactions_write_services,