fix: correct field error labels in purchase confirm action

The validateRequired() calls had wrong label strings — each field was
labelled with the PREVIOUS field's name, causing confusing error messages
like 'Nomor WhatsApp wajib diisi' when the Bank Name field was empty.

Before:
  bankName:          validateRequired('Nomor WhatsApp', bankName)
  bankAccountNumber: validateRequired('Nama Bank', bankAccountNumber)
  bankAccountName:   validateRequired('Nomor Rekening', bankAccountName)

After (matching the form field labels):
  bankName:          validateRequired('Nama Bank', bankName)
  bankAccountNumber: validateRequired('Nomor Rekening', bankAccountNumber)
  bankAccountName:   validateRequired('Nama Pemilik Rekening', bankAccountName)

All 116 tests pass.

Author: wheeljackz

app/routes/dashboard.purchase.confirm.tsx

@@ -75,9 +75,9 @@ export const action: ActionFunction = async ({ request }) => {
   }
 
   const fieldErrors = {
-    bankName: validateRequired('Nomor WhatsApp', bankName),
-    bankAccountNumber: validateRequired('Nama Bank', bankAccountNumber),
-    bankAccountName: validateRequired('Nomor Rekening', bankAccountName),
+    bankName: validateRequired('Nama Bank', bankName),
+    bankAccountNumber: validateRequired('Nomor Rekening', bankAccountNumber),
+    bankAccountName: validateRequired('Nama Pemilik Rekening', bankAccountName),
     amount: validateRequired('Nominal', amount),
   }