Journal Entry validation only checked party details when an account was
of type Receivable/Payable, but never restricted setting a Party Type or
Party against accounts of other types. This regressed v14 behavior where
party info could only be captured for Receivable/Payable accounts.
Add a branch to validate_party() that throws when a Party Type or Party
is set on an account that is not Receivable/Payable, with a clear message.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>