Provide APIs for organizers to monitor ticket sales and attendees

[GideonBature]

Description

Provide APIs for organizers to monitor ticket sales and attendees. This PR introduces new endpoints that allow event organizers to retrieve comprehensive information about their events, including ticket sales statistics, revenue data, and attendee details.

Related Issues

Closes #360

Changes Made

• Added OrganizerController with endpoint to get organizer's events (GET /organizer/:id/events)
• Created OrganizerService with business logic for fetching organizer events
• Implemented comprehensive DTOs for Event, Attendee, EventStats, and OrganizerEventsResponse
• Added authorization check to ensure organizers can only access their own events
• Integrated new controller and service into the main AppModule
• Added mock data structure with sample events, attendees, and sales statistics

How to Test

1. Start the application using npm run start
2. Make a GET request to http://localhost:3000/organizer/org1/events
3. Verify the response includes:
   • Event details (title, description, date, location)
   • Ticket sales statistics (sold, remaining, revenue)
   • Attendee information (name, email, purchase date)
4. Test authorization by trying to access events with a different organizer ID
5. Confirm a 403 Forbidden error is returned for unauthorized access attempts

Screenshots (if applicable)

N/A - Backend API changes only

Checklist

• My code follows the project's coding style.
• I have tested these changes locally.
• Documentation has been updated where necessary.

[BigBen-7]

LGTM