Restructure backend into modular API layers with admin/organizador/invitados routes, add role-based middleware, flatten module models, and update build scripts

packages/legacy/src/core/services/notification-provider.interface.ts

@@ -0,0 +1,5 @@
+export interface NotificationProvider {
+  send(options: { to: string; subject: string; body: string; metadata?: any }): Promise<void>;
+}
+
+export type NotificationChannel = 'email' | 'whatsapp' | 'sms' | 'custom';