PromotionCreateRequestMultipart

{
    "title": "Hero Banner",
    "description": "Big savings!",
    "ctaUrl": "https://example.com/deals",
    "placement": "homepage",
    "startDate": "2025-10-17T00:00:00",
    "endDate": "2025-10-31T23:59:59",
    "priority": 0,
    "isActive": true,
    "imageFile": "string",
    "imageUrl": "https://cdn.example.com/banners/hero.png"
}