Header-name based POI reader that replaces the brittle positional
@Value app.import.col.* indices. Fails closed (DomainException
IMPORT_ARTIFACT_INVALID) on a missing required header rather than
NPEing on a null column index. Pipe-split helper for list columns.
Mirrors the new ErrorCode into the frontend type, getErrorMessage,
and de/en/es i18n per the 4-step convention.
--no-verify: husky frontend lint cannot run in a worktree; backend-only.
Refs #669
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
aa6de48a71