Let \( f : \left[ -\dfrac{\pi}{2}, \dfrac{\pi}{2} \right] \to \mathbb{R} \) be a differentiable function such that \( f(0) = \dfrac{1}{2} \). If the \( \displaystyle \lim_{x \to 0} \dfrac{x \int_{0}^{x} f(t)\,dt}{e^{x^{2}} - 1} = \alpha \), then \( 8\alpha^{2} \) is equal to: