If for \( \theta \in \left[ -\dfrac{\pi}{3}, 0 \right] \), the points \( (x, y) = \left( 3 \tan \left( \theta + \dfrac{\pi}{3} \right), \, 2 \tan \left( \theta + \dfrac{\pi}{6} \right) \right) \) lie on \( xy + \alpha x + \beta y + \gamma = 0 \), then \( \alpha^2 + \beta^2 + \gamma^2 \) is equal to: