feat: Phase 1 — remove Stripe, switch to e-Transfer

- Drop stripe_payment + stripe_sdk deps; delete stripe pay pages/widgets
- New ETransferPay widget: shows payment@wisetronic.com + R#<orderId> remark
- goPayment stripe/native branches now route to e-Transfer
- pay_now widgets: strip saved-cards section & dead nativePay logic
- my_cards pages rewritten as e-Transfer info (route kept)
- models/utils/constants cleaned of stripe; env constraint -> Dart 3

See UPGRADE_NOTES.md. (Null-safety migration is Phase 3; deps upgrade Phase 2.)

lib/utils/util_web.dart

@@ -16,11 +16,10 @@ import '../generated/l10n.dart';
 import '../models/comment.dart' as mComment;
 import '../models/order.dart';
 import '../models/payment_platform.dart';
-import '../models/stripe_payment_method.dart';
 import '../models/user.dart';
 import '../store/actions.dart';
 import '../store/store.dart';
-import '../pages/stripe_pay_web.dart';
+import '../widgets/general/e_transfer_pay.dart';
 import 'http_util.dart';
 import 'utils.dart';
 
@@ -252,7 +251,6 @@ class Util {
       PaymentPlatform paymentPlatform, {
         bool googlePay=false,
         bool applePay=false,
-        StripePaymentMethod stripePaymentMethod,
       }) {
     switch(paymentPlatform.code) {
       case Constants.PAYMENT_METHOD_CODE_SQUARE:
@@ -276,7 +274,7 @@ class Util {
       case Constants.PAYMENT_METHOD_CODE_STRIPE:
         Navigator.pushReplacement(context, MaterialPageRoute(
             builder: (BuildContext context) {
-              return StripePayWeb(order, paymentPlatform, stripePaymentMethod: stripePaymentMethod,);
+              return ETransferPay(order: order);
             }
         ));
         break;