Header matching in searchDataInExcel() was case-insensitive but not
whitespace-tolerant, so a header like " SOME_CHAR" (an easy defect to
pick up via copy-paste from another spreadsheet/system) was reported as
a missing column and aborted the whole upload.
- trim() the cell value before matching, alongside the existing
toLowerCase() normalization
- add spreadsheet-util.spec.ts (no prior spec file existed) covering
the trimmed match and a regression guard that a genuinely different
header is still correctly reported missing
- add a Cypress case + fixture in excel.cy.ts covering the same defect
end to end
