Is one who does not wake up for Qiyam al-Layl and Fajr—despite setting an alarm—sinful, and is his not waking up a sign that he is not worthy of Qiyam al-Layl?

It is from Allah Almighty's mercy that whoever genuinely intends to perform an act of obedience, its reward is written for him, even if he does not carry it out, provided he was prevented from doing so by an impediment such as sleep or illness. Therefore, whoever intends to perform Qiyam al-Layl (night prayer) but is overcome by sleep, what he intended is written for him, and his sleep becomes a charity for him. A Muslim should intend to perform Qiyam al-Layl when going to sleep to attain this virtue. There is no sin upon a sleeping person for missing the Fajr prayer, as accountability is lifted from him. It is recommended to make up for missed Qiyam al-Layl. If a Muslim misses his portion of Qiyam al-Layl due to sleep or an excuse, and he recites it between the Fajr prayer and the Dhuhr prayer, it is written for him as if he had recited it during the night. Among the things that help with Qiyam al-Layl are repenting from sins, taking a sufficient rest during the day, eating less, and sleeping early.