Better document "reset sequence" feature

I changed the "initial number" in a number pattern but wasn’t aware that I also needed to manually reset the sequence. This action is hidden in the dropdown, so if you don’t open it, you won’t know it’s necessary.

A simple solution would be to improve the documentation for this feature:

- Add a note near the "initial number" field explaining that a reset is required and indicating where to find it.
- Display a message when the number pattern is saved as a reminder.