Fix: handle NOTSET payment mode during invoice deserialization

Changes:

- Added support for PaymentMode::NOTSET in string-to-enum conversion
  to prevent invoice deserialization failures during system startup
- Improved invoice table column labels and spacing for better readability
  and alignment in invoice display screens

Fixes #1789

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/utilities/Enums.h

@@ -137,6 +137,10 @@ namespace util
         {
             return PaymentMode::OFFLINE;
         }
+        if (value == "NOTSET")
+        {
+            return PaymentMode::NOTSET;
+        }
         throw std::invalid_argument("Invalid PaymentMode string");
     }