Walaykumsalaam.
It is not prescribed in Islam to celebrate the night of the fifteenth of Sha‘baan, whether that is by spending the night in prayer, dhikr and reading Qur’aan, or by distributing sweets or giving food to people and so on.
It is not known in the saheeh Sunnah that this night is to be singled out for acts of worship or customs.
The night of the fifteenth of Sha‘baan is just like any other night.
Allah knows best