Transaction authorize and capture without duplicate processing

Transactions: authorize and capture handling now skip duplicate work when a payment is already in progress or already at the reported status, so overlapping updates are less likely to rerun the same step.

• Repeat status updates for an authorization that has not changed are ignored, so polling and webhooks stay stable on duplicate events.
• Capture moves to a processing state before work begins, so retried or overlapping requests cannot start another capture on the same payment.