Protection:
If you insert the battery carefully in the correct direction in an ESD protected area, then no need for extra effort.
* If you expect ESD, then you need to add ESD protection.
* If you install the battery the other way round then you need to install reverse voltage protection.
Along with these observations, I would add one more: In choosing the coin holder, pay attention to those that allow Vbat making contact before the GND during battery insertion, as this may cause problems depending on the robusteness of the internal circuit of the uC in face to ESD and/or if proper care has not been taken at assembly time; prefer those whose battery negative surface always makes contact first to the holder terminal.