Updated description and been added the source code.

@tonnerre33,
Thank you for your interest to my device.
The fuse installed to protect the mains 220V from short circuit in the device. Phase need to be connected to the device through a circuit breaker. It will protect from dangerous potential and this allows the lamps to be served safely. But you're right. It would be properly to put the fuse on the phase.

Looking at my experience I can say that never had a problem without varistor. But probably in the future I will add it to the board.

@Samuel235, It is just my first project and it has some weaknesses. But thanks for the comment, I will use it in future.