[REFACTOR] Create unified NotificationService interface

[aniebietafia]

Problem

The application handles user notifications in an ad-hoc, siloed manner:

• Push notifications are sent via NotificationController.java.
• SMS is handled by smsservice.
• Emails are orchestrated by EmailOrchestratorService.

There is no common notification layer that allows sending a notification to a user using their preferred channel (email, SMS, or push).

Proposed Solution

Create a unified NotificationService interface. This service acts as a single gateway for dispatching notifications, resolving user preferences at runtime to determine whether to route via email, SMS, push notifications, or all.

User Stories

• As a system event, I want to trigger a single dispatch call notificationService.send(userId, alert) and let the system resolve user channel choices automatically.

Acceptance Criteria

• Interface NotificationService is defined.
• A dispatcher class routes message requests based on user preferences.
• Code redundancy across notification layers is minimized.

Tasks

• Define the unified interface.
• Implement the dispatcher routing logic.
• Integrate user preference lookup.