Is reciting the Quran during the night prayer considered part of the daily portion, such that it is combined with the daytime reading from the Mus'haf to be counted as a complete portion?

What you recite is attributed to the time it occurred. The portion you read during the day is attributed to its time, and what you recited at night is likewise attributed to it. Thus, you recite half a juz' at night and half a juz' during the day, and your daily portion (wird) is one juz' per day and night. We advise you to recite the Qur'an frequently.