- Add excelize v2 for XLSX parsing
- Auto-detect column indices from header row using common DD checklist
naming conventions (section/category/topic, item#/ref/no, description/
request/document, priority/urgency/criticality)
- Detect file type by extension + PK magic bytes (xlsx is a zip)
- Smart priority mapping: critical/urgent→high, nice/optional→low
- Fall back to positional parsing (col 0=section, 1=item#, 2=desc) if
headers don't match known patterns
- Update modal label: 'Excel .xlsx or CSV — columns auto-detected'