feat(registry): add payout sync support with webhook events

[matingathani]

Summary

The payouts table is created by migrations but never populated — payout was missing from RESOURCE_MAP, PREFIX_RESOURCE_MAP, and SUPPORTED_WEBHOOK_EVENTS.

Changes:

• Added payout entry to RESOURCE_MAP (order 20, sync: true, isFinalState for paid/failed/canceled)
• Added po_: prefix to PREFIX_RESOURCE_MAP for ID-based routing
• Added payout webhook events to SUPPORTED_WEBHOOK_EVENTS:
  • payout.canceled
  • payout.created
  • payout.failed
  • payout.paid
  • payout.reconciliation_completed
  • payout.updated

This enables payment reconciliation use-cases: payment_intents → charges → payouts all sync correctly now.

Test plan

• Run backfill sync and verify payouts table is populated
• Trigger payout.paid webhook and verify the payout row is upserted
• Verify getResourceFromPrefix("po_abc") resolves to payout
• getSupportedEventTypes() includes the new payout events

Closes #151

[Copilot]

Pull request overview

Adds Stripe payout as a first-class syncable resource so the existing payouts table can be populated via backfill sync and webhook-driven upserts, completing the reconciliation chain (payment_intents → charges → payouts).

Changes:

• Register payout in the sync RESOURCE_MAP (list/retrieve, backfill order, final-state detection).
• Add po_ to PREFIX_RESOURCE_MAP for ID-prefix routing to payout.
• Expand SUPPORTED_WEBHOOK_EVENTS to include payout.* event types.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/sync-engine/src/types.ts	Adds payout.* webhook event types to the allowed/supported webhook event list.
packages/sync-engine/src/resourceRegistry.ts	Registers payout as a syncable resource and adds po_ prefix routing to resolve payout IDs.

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