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/utils.dart

@@ -291,39 +291,6 @@ class Utils {
     return amount.toStringAsFixed(decimalPlace);
   }
 
-  static void createOrUpdateStripePaymentMethod(
-    String paymentMethodId,
-    String cardBrand,
-    String paymentMethodType,
-    String cardCountry,
-    int cardExpMonth,
-    int cardExpYear,
-    String cardFunding,
-    String cardLast4,
-  ) {
-    HttpUtil.httpPost(
-      'v1/create-update-stripe-payment-method',
-      (response) {
-        if (response.statusCode == 200) {
-          print(
-              'create or update customer stripe payment method success. ${response.data}');
-        }
-      },
-      body: {
-        'payment_method_id': paymentMethodId,
-        'card_brand': cardBrand,
-        'payment_method_type': paymentMethodType,
-        'card_country': cardCountry,
-        'card_exp_month': cardExpMonth,
-        'card_exp_year': cardExpYear,
-        'card_funding': cardFunding,
-        'card_last4': cardLast4,
-      },
-      isFormData: true,
-    ).catchError((error) {
-      print('Error: ${error}');
-    });
-  }
 
   static showSubmitDialog(BuildContext context) {
     showDialog(
@@ -900,48 +867,7 @@ class Utils {
     }
   }
 
-  static void stripePaymentIntent(Order order, String customerId, String paymentMethodId, String cardType,
-      OnSuccess onSuccess, OnError onError,
-      {
-        String cardBrand,
-        String cardCountry,
-        int cardExpMonth,
-        int cardExpYear,
-        String cardFunding,
-        String cardLast4,
-      }) {
 
-    HttpUtil.httpPost('v1/stripe-payment-intent',
-      onSuccess,
-      body: {
-        'order_id': order.id,
-        'pay_amount': order.totalPrice,
-        'customer_id': customerId == null ? '' : customerId,
-        'payment_method_id': paymentMethodId,
-        'payment_method_type': cardType,
-        'card_brand': cardBrand,
-        'card_country': cardCountry,
-        'card_exp_month': cardExpMonth,
-        'card_exp_year': cardExpYear,
-        'card_funding': cardFunding,
-        'card_last4': cardLast4,
-      },
-      isFormData: true,
-    ).catchError(onError);
-  }
-
-  static void stripeChargedSuccess(Order order, String paymentMethodId,
-      String paymentIntentId, OnSuccess onSuccess, OnError onError) {
-    HttpUtil.httpPost('v1/stripe-charged-success',
-        onSuccess,
-        isFormData: true,
-        body: {
-          'order_id': order.id,
-          'payment_method_id': paymentMethodId,
-          'payment_intent_id': paymentIntentId,
-        }
-    ).catchError(onError);
-  }
 
   static int getProductLineInOrder(CartInfo cartInfo) {
     int qty = 0;