Payments fixes

Stripe webhook: No signatures found matching the expected signature
StripeSignatureVerificationError: No signatures found matching the expected signature for payload
CursorBoltReplitv0Payments

Payment succeeds but the user isn't upgraded
Stripe shows the payment as succeeded but the app still shows the free plan
LovableBoltCursorPayments

No such price / No such customer (test vs live mode mix-up)
StripeInvalidRequestError: No such price: 'price_...'
CursorBoltv0LovablePayments