report_service uses 'summary'/'weekly'/'keine_rm'/'gutachten' but
excel_export expected 'totals'/'weeks'/'keine_rueckmeldung'/
'gutachten_gesamt'. Also fix nested gesamt dict access in sheet3
and icd_codes path from sheet5.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>