What is the ruling on naming a newborn after a Companion's kunya as a blessing, and is there any Shar'i (Islamic legal) evidence permitting or prohibiting that?

It is from the Sunnah to be named and to take a kunya with beautiful names. The best names are those of the Prophets and the Companions. Therefore, a Muslim should name themselves with their names and take their kunyas, as this is what the Companions and the righteous predecessors used to do. From this perspective comes the desirability of naming a girl "Al-Zahra" in blessing and emulation of the Prophet's daughter (peace be upon him).