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WorkbookFactory throws ODFNotOfficeXmlFileException on .ods files — Apache POI does not support ODF format at all. Replace ODS reading with a direct content.xml parser using Java's built-in ZipFile + DOM API (no new dependency). ODS is a ZIP archive; the spreadsheet lives in content.xml as standard ODF XML. Also refactors the import pipeline to decouple file reading from import logic: both ODS and XLSX paths now produce List<List<String>> which is processed by format-agnostic row logic. XLSX date cells are now converted to ISO strings before processing. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>