Two vectors, u and v, are such that

\(\mathbf{u} = \begin{pmatrix} q \\ 2 \\ 6 \end{pmatrix}\) and \(\mathbf{v} = \begin{pmatrix} 8 \\ q-1 \\ q^2-7 \end{pmatrix}\),

where \(q\) is a constant.

(i) Find the values of \(q\) for which \(\mathbf{u}\) is perpendicular to \(\mathbf{v}\).

(ii) Find the angle between \(\mathbf{u}\) and \(\mathbf{v}\) when \(q = 0\).