dg-Hecke duality and tensor products

We continue our study of the monoidal category $D(G)$. At the level of cohomology we transfer the duality functor to the derived category of Hecke dg-modules. In the process we develop a more general and streamlined approach to the anti-involution first defined by Ollivier and Schneider. We also verify that the tensor product on $D(G)$ corresponds to an operadic tensor product on the dg-side. This uses a result of Schn\"{u}rer on dg-categories with a model structure.