Does missing Fajr prayer due to sleep until sunrise, then praying and repenting, necessitate performing ghusl or reaffirming the Shahadatayn?

If your mother woke you up after the time for prayer had begun, and you intentionally continued sleeping until the time expired, then you are sinful. It is sufficient for you to make up the prayer and repent. You are not required to perform ghusl or to recite the Shahadatayn anew, because intentionally missing a single prayer until its time expires is not considered an act of disbelief (kufr). However, if your return to sleep was before the prayer time began, or due to being overcome by sleep, then there is no sin upon you.