Add admin transaction cancellation without deleting history.

Cancelled transactions are excluded from paid totals and due-date
calculations while remaining visible for audit purposes.

utils/paymentAmount.test.js

@@ -73,6 +73,16 @@ describe('paid vs pending transactions', () => {
     assert.equal(isPaidTransaction({ status: 'pending', amount: 2_000_000 }), false);
     assert.equal(isPaidTransaction({ status: 'paid', amount: 8_000_000 }), true);
   });
+
+  it('ignores cancelled transactions in paid totals', () => {
+    const transactions = [
+      { amount: 5_000_000, status: 'paid', date: '2026-08-03' },
+      { amount: 5_000_000, status: 'cancelled' },
+      { amount: 2_000_000, status: 'pending', dueDate: '2026-08-23' }
+    ];
+    assert.equal(sumPaidTransactions(transactions), 5_000_000);
+    assert.equal(isPaidTransaction({ status: 'cancelled', amount: 5_000_000, date: '2026-08-03' }), false);
+  });
 });
 
 describe('sanitizeNotes', () => {