refactor: organize backend by business responsibility

src/modules/investments/operations/operations.api.ts

@@ -0,0 +1,3 @@
+// Public cross-module surface. Nest providers are exported by the matching module.
+export { BrokerageOperationDto } from './presentation/brokerage-operation.dto';
+export { BrokerageOperationsService } from './application/brokerage-operations.service';