Elliptic estimates on a compact domain

Question

Let $\Omega \subset \mathbb{R}^n$ be a ball with boundary. Consider the operator $-\Delta + V$ on $\Omega$, where $\Delta$ is the Dirichlet Laplacian and $V$ is a positive smooth potential. Let $u$ solve the PDE $-\Delta u + V u = \mu u$, where $\mu > 0$ is a constant. Do we have $\| u\|_{L^\infty} \leq C\| u\|_{L^2}$, where $C$ is a positive constant? What does this constant depend on?