Issue: Update dbFieldMapper Utility for New Schema Fields

[NahomAlemu]

Description

The dbFieldMapper.ts utility needs to handle the new field mappings between backendresponse and frontend types. The cover photo and document fields now return Media objects or UUIDs instead of direct URLs. Without this update, events won't display cover photos or documents correctly.

Components Affected:

• EventCard.tsx
• HomeEventsCard.tsx
• UpcomingEvent.tsx
• EventGetter.tsx
• event-detail/page.tsx

Tasks

• Add mapping for coverPhotoId ↔ eventCoverPhoto (backward compatibility)
• Add mapping for documentId ↔ eventDocument (backward compatibility)
• Handle nested coverPhoto and document Media objects in response
• Extract s3Url from Media objects for display components
• Update nsc-events-nextjs/tests/unit/dbFieldMapper.test.tsx with new test
  cases
• Ensure 100% test coverage maintained

Visual Aids

Expand ⬇️

**Transformation Example:**
```typescript
// Backend Response
{
  coverPhotoId: "uuid-123",
  coverPhoto: {
    id: "uuid-123",
    s3Url: "https://s3.../image.jpg",
    originalName: "photo.jpg"
  }
}

// Frontend Needs
{
  eventCoverPhoto: "https://s3.../image.jpg"  // For backward compat
  coverPhotoId: "uuid-123"                     // New field
}