Stack Safety

How stack buffer overflow happens in C PMenu_Do_Update() and how to fix it

A stack buffer overflow in `PMenu_Do_Update()` within `src/menu/menu.c` allowed repeated unchecked `sprintf()` calls to overflow a fixed 1400-byte stack buffer when menu entries contained long text strings. The fix replaces every `sprintf(string + strlen(string), ...)` call with `snprintf(string + len, sizeof(string) - len, ...)`, tracking remaining buffer space and preventing writes beyond the buffer boundary.