Simplify payment updates by removing race condition logic

- Remove complex optimistic locking and version-based updates
- Simplify payment status updates assuming providers don't send duplicates
- Remove version field from Payment type and collection schema
- Clean up webhook detection logic in payment hooks
- Streamline updatePaymentStatus function for better maintainability

Payment providers typically don't send duplicate webhook requests, so the
complex race condition handling was unnecessary overhead.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/plugin/types/payments.ts

@@ -48,7 +48,6 @@ export interface Payment {
     | boolean
     | null;
   refunds?: (number | Refund)[] | null;
-  version: number;
   updatedAt: string;
   createdAt: string;
 }