In $△ABC$ shown, $AB=BC=12$ and $m\angle A=30^{\circ }$. If $\overline{BD}$ is an altitude to $\overline{AC}$, what is the area of $△ABC$?

(A diagram similar to the original would be provided, showing an isosceles triangle ABC with altitude BD, where AB=BC=12 and angle A = 30 degrees.)