changed primary color usage to fix the color bug in dark mode

Changed Theme.of(context).primaryColor to Theme.of(contex).colorScheme.primary to make dark mode work properly.

lib/features/fund_transfer/screens/transaction_pin_screen.dart

@@ -94,7 +94,7 @@ class _TransactionPinScreenState extends State<TransactionPinScreen> {
             shape: BoxShape.circle,
             border: Border.all(color: Theme.of(context).primaryColor, width: 2),
             color: index < _pin.length
-                ? Theme.of(context).primaryColor
+                ? Theme.of(context).colorScheme.primary
                 : Colors.transparent,
           ),
         );
@@ -142,11 +142,7 @@ class _TransactionPinScreenState extends State<TransactionPinScreen> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text(
-          AppLocalizations.of(context).tpin,
-          style:
-              const TextStyle(color: Colors.black, fontWeight: FontWeight.w500),
-        ),
+        title: Text(AppLocalizations.of(context).tpin),
         centerTitle: false,
       ),
       body: _loading