The #4 cost side used 'date(COALESCE(invoice_date, created_at)) BETWEEN ...'
and 'date(created_at) BETWEEN ...'. The mocked unit tests never execute the
SQL, so the Postgres failure (date()/COALESCE(date,timestamp)) slipped through
and surfaced as a 500 on the live tax report. Replaced with plain range
comparisons (col >= from AND col <= '<to> 23:59:59.999') — valid on both PG and
SQLite, inclusive of the whole end day. Same fix applied to ledgerService
buildPostings (the Treuhänder export would have 500'd identically).