- Add mergeFiles() method in ExtractorService to combine downloaded batch files
- Add saveMergedOrders() method to output full 31-column Excel format
- Update recordCount to return actual material record count
- Add missing field mappings in OrderHeader type and ExcelParser:
- factory, materialStatus, planNumber, materialType
- department, remark, createDate, approveDate
- Output file named with timestamp: merged_YYYYMMDDHHMMSS.xlsx
Co-Authored-By: Claude (glm-5) <noreply@anthropic.com>