ASK-20261001-33: api_receivables counts only rows with a non-blank counterparty (monthly aggregate rows stay in table but out of the collection page cards/aging/detail/owners); BALANCE_SNAPSHOT_SOURCES gains hanke_ar (default skip, no per-customer overdue alerts). New pytest file covers aggregate-row exclusion, e2 baseline digitwise, snapshot registration. (cherry picked from commit 475f78bc8c5f67f2716c721172a88ff89ec58227)