What is the ruling on supererogatory prayers (nawafil) at sunrise and sunset, and does this include the two rak'ahs of seeking forgiveness, circumambulation (tawaf), and the prostration of recitation (sajdat al-tilawah)? And what is the evidence for that?

Prostration of recitation (Sujud al-Tilawah) is permissible during the prohibited times for prayer because it is not a prayer. Even if it were considered a prayer, it would be among those with a specific cause. As for the two rak'ahs of repentance, it is permissible to perform them during the prohibited times because they are a prayer with a specific cause, which is when a Muslim commits a sin, then rises, purifies himself, prays two rak'ahs, and then seeks Allah's forgiveness.