feat: drive visible payment methods from enabled providers

frontend/src/i18n/locales/en.ts

@@ -4757,6 +4757,7 @@ export default {
         supportedTypesHint: 'Comma-separated, e.g. alipay,wxpay',
         refundEnabled: 'Allow Refund',
         allowUserRefund: 'Allow User Refund',
+        enableConflict: '{method} already has an enabled provider instance: {provider}. Disable the existing instance before switching.',
       },
       balanceNotify: {
         title: 'Balance Low Notification',
@@ -5612,6 +5613,7 @@ export default {
       alipayMobileUnavailable: 'This page could not hand off to Alipay.',
       alipayMobileOpenHint: 'Allow the current page to open the Alipay app, or retry from the system browser.',
       PENDING_ORDERS: 'This provider has pending orders. Please wait for them to complete before making changes.',
+      PAYMENT_PROVIDER_CONFLICT: 'Another enabled provider instance is already serving this payment method. Disable it before continuing.',
     },
     stripePay: 'Pay Now',
     stripeSuccessProcessing: 'Payment successful, processing your order...',

frontend/src/i18n/locales/zh.ts

@@ -4921,6 +4921,7 @@ export default {
         supportedTypesHint: '逗号分隔，如 alipay,wxpay',
         refundEnabled: '允许退款',
         allowUserRefund: '允许用户退款',
+        enableConflict: '{method} 已有启用中的服务商实例：{provider}。请先停用现有实例后再启用或切换。',
       },
       balanceNotify: {
         title: '余额不足提醒',
@@ -5800,6 +5801,7 @@ export default {
       alipayMobileUnavailable: '当前页面未成功跳转到支付宝。',
       alipayMobileOpenHint: '请允许当前页面打开支付宝 App，或改用系统浏览器重新发起支付。',
       PENDING_ORDERS: '该服务商有未完成的订单，请等待订单完成后再操作',
+      PAYMENT_PROVIDER_CONFLICT: '该支付方式已有其他启用中的服务商实例，请先停用后再继续。',
     },
     stripePay: '立即支付',
     stripeSuccessProcessing: '支付成功，正在处理订单...',