Greetings Mubashir.
I believe in the context of all Qoran, GOD does not forgive Idolworship"Shirk If maintained until death. That is what 4:48 is stating.
One can always repent and will find that GOD is Forgiver most Merciful.
In the case of the " Calf" Those who repented were forgiven:
2:54
Recall that Moses said to his people, "O my people, you have wronged your souls by worshiping the calf. You must repent to your Creator. You shall kill your egos. This is better for you in the sight of your Creator." He did redeem you. He is the Redeemer, Most Merciful.
وَإِذ قالَ موسىٰ لِقَومِهِ يٰقَومِ إِنَّكُم ظَلَمتُم أَنفُسَكُم بِاتِّخاذِكُمُ العِجلَ فَتوبوا إِلىٰ بارِئِكُم فَاقتُلوا أَنفُسَكُم ذٰلِكُم خَيرٌ لَكُم عِندَ بارِئِكُم فَتابَ عَلَيكُم إِنَّهُ هُوَ التَّوّابُ الرَّحيمُ
So they were forgiven.
There is no contradiction.
GOD bless you.
Peace.
"