Complete unfinished payouts (owner-gated)

Heals the crash-safety net. For each unfinished obligation it decides safely: if the recipient balance already rose by the payout amount the payout landed and the row is cleared; if the balance is provably unchanged the payout never happened and can be completed; anything ambiguous is left pending for manual review, so it can never double-pay. Obligations younger than ten minutes are skipped because their payout may still be broadcasting. Requires the owner key; DRY unless {"live":true}. A keeper runs this automatically every five minutes.