curl -X GET "https://staging-api.loyalty.lt/en/shop/products/categories" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_api_secret"

{
  "success": true,
  "code": 200,
  "request_id": "550e8400-e29b-41d4-a716-446655440000",
  "data": {
    "categories": [
      {
        "id": 1,
        "name": "Electronics",
        "slug": "electronics",
        "children": [
          {
            "id": 2,
            "name": "Phones",
            "slug": "phones",
            "children": []
          },
          {
            "id": 3,
            "name": "Laptops",
            "slug": "laptops",
            "children": []
          }
        ]
      }
    ],
    "flat_list": [
      { "id": 1, "name": "Electronics", "level": 0 },
      { "id": 2, "name": "-- Phones", "level": 1 },
      { "id": 3, "name": "-- Laptops", "level": 1 }
    ],
    "total": 45
  },
  "message": "Categories retrieved successfully"
}