what is the maximum angle turned by a car's front wheels ?
There is no single answer. The maximum angle is dictated by how much room there is physically available. My experience is with medium and heavy duty trucks. These vehicles have wheel sizes and axle tracks dictated my either legal or market requirements.
Inboard of the wheels you have the front springs and the frame. These usually are the hard points which determine the maximum angle. However on one side of the vehicle is a draglink which has to fit between the frame and wheel, and so reduces the allowable angle. Obviously smaller wheels allow for greater articulation.
Next you need to consider the angles between all the steering components. If there is a risk of inverting any of the connections you need to restrict the maximum angles further.
I suspect similar restrictions apply to cars and the ability to miss the body structure or suspension/steering components.