Нормализатор Unpivot XLSX

# 1) Request a presigned URL → returns { uploadUrl, storageKey }
curl -X POST 'https://api.elysiatools.com/api/upload/presign/xlsx-unpivot-normalizer' \
  -H 'Content-Type: application/json' \
  -d '{"filename":"excelFile.ext","contentType":"application/octet-stream","size":12345}'

# 2) PUT the file bytes directly to the presigned uploadUrl
curl -X PUT '<presigned uploadUrl>' \
  --data-binary @/path/to/file.ext

# 3) Call the tool, passing the returned storageKey for each file field
curl -X POST 'https://api.elysiatools.com/ru/api/tools/xlsx-unpivot-normalizer' \
  -F 'excelFile=uploads/2026/01/01/your-tool-1700000000000-abc123.ext' \
  -F 'sheetName=Sheet1' \
  -F 'headerRow=1' \
  -F 'idColumns=name,region' \
  -F 'valueColumns=Jan,Feb,Mar' \
  -F 'keyColumnName=month' \
  -F 'valueColumnName=value' \
  -F 'outputMode=xlsx' \
  -F 'dropEmptyValues=true' \
  -F 'parseNumbers=true'