feat(1099): carry PayeeId through expense create/update/read

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>

API/ROLAC.API/DTOs/Expense/ExpenseDtos.cs

@@ -35,6 +35,7 @@ public class ExpenseListItemDto
     public string?  ReviewedByName { get; set; }       // resolved Member full name, email fallback
     public DateTimeOffset? ReviewedAt { get; set; }
     public string?  ReviewNotes { get; set; }          // reject reason (or approval note)
+    public int?     PayeeId     { get; set; }
 }
 
 public class ExpenseDto : ExpenseListItemDto
@@ -66,6 +67,7 @@ public class CreateExpenseRequest
     [MaxLength(50)] public string? CheckNumber { get; set; }
     [Required] public DateOnly ExpenseDate { get; set; }
     public string?  Notes { get; set; }
+    public int?     PayeeId { get; set; }
 }
 public class UpdateExpenseRequest : CreateExpenseRequest { }