use descriptive top-level message for direct payments

Keep provider-specific details in data.message and return a stable, human-readable top-level success message for /payments/direct responses.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web_server/handlers/arifpay.go

@@ -350,7 +350,7 @@ func (h *Handler) InitiateDirectPayment(c *fiber.Ctx) error {
 	}
 
 	return c.JSON(domain.Response{
-		Message: result.Message,
+		Message: "Direct payment initiated successfully",
 		Data:    result,
 	})
 }