Implement Notifications and Updates

[reyraa]

Implement the API to notify fans of updates to projects they have contributed to or are following.

Parent

• Add support for projects #7

Acceptance Criteria:

• API endpoint to create notifications for project updates.
• Ensure notifications are sent to fans based on their preferences (e.g., email, in-app).
• API endpoint for fans to manage their notification preferences.
• Documentation of the notification system and related API endpoints.