Deadline CSV-to-JSON conversion: verify keys and IDs

Under a deadline, inspect the CSV header for duplicate or empty names before converting. Preserve the original file, then check that JSON object count matches the data rows and that important values—especially leading-zero IDs, dates, and large numbers—have the intended types. Test a row with quoted commas or line breaks. Parse the output once more and compare key records with the source. A generated file is useful only if consumers can interpret its keys and values correctly.