feat: add image upload for health package

backend/prisma/migrations/20260518055117_health_checkup_optional_image_field/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "HealthPackage" ADD COLUMN     "image" TEXT;

backend/prisma/schema.prisma

@@ -241,6 +241,7 @@ model HealthPackage {
   slug         String              @unique
   description  String?
   price        Decimal?            @db.Decimal(10, 2)
+  image        String?
   discountedPrice Decimal?         @db.Decimal(10, 2)
   
   inclusions   Json                @default("{}")