feat(expenses): add transactional expense case events

server/src/app/models/__init__.py

@@ -8,6 +8,7 @@ from app.models.budget import BudgetAllocation, BudgetReservation, BudgetTransac
 from app.models.employee_change_log import EmployeeChangeLog
 from app.models.employee_behavior_profile import EmployeeBehaviorProfileSnapshot
 from app.models.employee import Employee
+from app.models.expense_case import BusinessEvent, ExpenseCase, ExpenseCaseLink
 from app.models.few_shot_sample import FewShotSample
 from app.models.financial_record import (
     AccountsPayableRecord,
@@ -47,6 +48,9 @@ __all__ = [
     "BudgetReservation",
     "BudgetTransaction",
     "Employee",
+    "ExpenseCase",
+    "ExpenseCaseLink",
+    "BusinessEvent",
     "EmployeeBehaviorProfileSnapshot",
     "EmployeeChangeLog",
     "ExpenseClaim",