feat: add supplier payment and allocation models, API, and frontend components

- Created `SupplierPayment` and `SupplierPaymentGRN` models for managing supplier payments and their allocations.
- Implemented API endpoints for listing and creating supplier payments.
- Developed frontend components for displaying and recording supplier payments, including a dialog for payment creation.
- Integrated GRN allocations into the payment creation process, ensuring total allocations match the payment amount.
- Added pagination and loading states for the payments list.

Distribution/Models/SupplierPayment.cs

@@ -0,0 +1,32 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    public class SupplierPayment : Template
+    {
+        public Guid FK_SupplierId { get; set; }
+        [ForeignKey("FK_SupplierId")]
+        public Supplier? Supplier { get; set; }
+
+        public decimal Amount { get; set; }
+
+        // Only Cash or Cheque are valid for outgoing payments. Credit is rejected at the service layer.
+        public PaymentMethod Method { get; set; }
+
+        // Cash: required. Null for Cheque.
+        public Guid? FK_BankAccountId { get; set; }
+        [ForeignKey("FK_BankAccountId")]
+        public BankAccount? BankAccount { get; set; }
+
+        // Cheque: required — the ChequePage this payment issued. Null for Cash.
+        public Guid? FK_ChequePageId { get; set; }
+        [ForeignKey("FK_ChequePageId")]
+        public ChequePage? ChequePage { get; set; }
+
+        public DateTime PaidAt { get; set; }
+        public Guid? PaidByUserId { get; set; }
+        public string? Notes { get; set; }
+
+        public ICollection<SupplierPaymentGRN> Allocations { get; set; } = [];
+    }
+}