feat(payment): 增加本地 Mock 支付渠道与缺失渠道提示

backend/internal/modules/payment/handler.go

@@ -12,6 +12,7 @@ import (
 	"hfb_sys/backend/internal/integrations/payment/shuncheng"
 	"hfb_sys/backend/internal/middleware"
 	"hfb_sys/backend/internal/modules/order"
+	"hfb_sys/backend/internal/modules/paymentconfig"
 	"hfb_sys/backend/pkg/response"
 
 	"github.com/gin-gonic/gin"
@@ -316,6 +317,13 @@ func writePaymentError(c *gin.Context, err error) {
 		response.ServiceUnavailable(c, "数据库未连接")
 	case errors.Is(err, ErrPaymentUnavailable):
 		response.Error(c, http.StatusBadGateway, "payment_unavailable", "支付渠道暂不可用")
+	case errors.Is(err, paymentconfig.ErrNoActiveConfigFound):
+		response.Error(
+			c,
+			http.StatusServiceUnavailable,
+			"payment_channel_missing",
+			"尚未配置可用的支付渠道，请在后台「支付配置」启用渠道；本地联调可使用 Mock 渠道",
+		)
 	case errors.Is(err, ErrPaymentCannotStart), errors.Is(err, order.ErrOrderCannotPay):
 		response.Error(c, http.StatusConflict, "payment_cannot_start", "当前订单不能支付")
 	case errors.Is(err, ErrRefundCannotStart):