Is there any Hadith where we should stand with our toes pointing straight ahead towards Qibla (not outwards as some people naturally stand) similar to when in prostration you should have the toes bent towards the Qibla as well as your fingers pointing towards the Qibla and when kneeling your fingers point towards Qibla as specific ahadith indicate?
There's a sahih hadith saying that the Prophet () used to prostrate his toes pointing to the qibla in the famous hadith of Abu Humaid as-Sa'idi أَبُو حُمَيْدٍ السَّاعِدِيُّ where he is explaining how the Prophet () used to pray:
I was sitting with some of the companions of Allah's Messenger (ﷺ) and we were discussing the way of praying of the Prophet. Abu Humaid As-Sa'idi said, "I remember the prayer of Allah's Messenger (ﷺ) better than anyone of you. I saw him raising both his hands up to the level of the shoulders on saying the Takbir; and on bowing he placed his hands on both knees and bent his back straight, then he stood up straight from bowing till all the vertebrate took their normal positions. In prostrations, he placed both his hands on the ground with the forearms away from the ground and away from his body, and his toes were facing the Qibla. On sitting In the second rak'a he sat on his left foot and propped up the right one, and in the last rak'a he pushed his left foot forward and kept the other foot propped up and sat over the buttocks."
(sahih al-Bukhari and also a version in sunan abi Dawod)
Scholars from this hadith deduced that it is recommended to do so while standing too, but one doesn't need to point at the qibla 100%, so your feet could form a "V", but this recommendation is definitely not a requirement for the validity of the prayer. You could even stand on one foot if you need to without invalidating the prayer. (see in Arabic islamweb #78835 and islamqa #181464)
In his (fath al-Bary) commentary on sahih al-Bukhari ibn Rajab also quoted a statement of Tawus طاوس saying that ibn 'Omar used to face the qibla with his whole body while praying and another of Salim the son of ibn 'Omar saying that his father disliked moving his hands/arms in a direction that doesn't point to the qibla. And considered facing the toes towards al-Ka'aba while standing in the prayer as a natural and basic state of prayer.
Ibn Hajar al-'Asqalani in his fath al-Bari commented on the "Chapter: One should keep the toes in the direction of the Qiblah" (search for the title 131 in "the call for adhan", where you may read: قَالَهُ أَبُو حُمَيْدٍ السَّاعِدِيُّ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ.) which al-Bukhari has created, but it includes only a link to abi Humaid as-Sai'di's hadith from above saying: That the author intended to show that it is recommended to face the qibla with all possible body parts.