Add int? PayeeId to CreateExpenseRequest (UpdateExpenseRequest inherits)
and to ExpenseListItemDto (so it round-trips to the form). Set e.PayeeId
unconditionally in CreateAsync and UpdateAsync so 1099 attribution is
independent of VendorPayment vs StaffReimbursement type. Map PayeeId in
both DTO projections: the paged-list lambda and GetByIdAsync.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Chris Chen