What is the ruling on praying the Isha and Fajr prayers very late due to daylight saving time? Is it permissible to combine prayers or delay them? And what is the effect of that on congregational prayer and Qiyam al-Layl (night vigil prayer)?

Combining the Maghrib and Isha prayers without a need is impermissible. However, one who cannot wake up for Isha may combine them. Combining prayers in mosques is not permissible unless there is a need for it. If they insist, pray Maghrib with them and complete Isha at its proper time. Sleeping before Isha is permissible out of necessity, and the time for Isha extends until Fajr. One who wakes up before Fajr and prays Isha and then Fajr has done well, as has one who wakes up for the Fajr prayer, even if it is a little after its time has begun. As for one who sleeps and does not wake up until after sunrise, there is no sin upon him, and he should pray what he missed. Qiyam al-Layl (night vigil prayer) is recommended and not obligatory, and congregational prayer for it is sunnah. It can also be performed at home.