feat:Implement Dynamic Smagorinsky SGS model for LES (Germano-Lilly, local approximation)

[Vamshimadhava]

Proposed Changes

Implements the CDynamicSmagorinskyModel::ComputeEddyViscosity_3D method in sgs_model.inl.

The implementation follows the Germano–Lilly dynamic procedure using a single-point approximation of the test filter, making it compatible with SU2's unstructured DG FEM solver architecture, which does not expose neighbor stencils at the SGS model level.

The Lilly least-squares estimator is used to compute the local Smagorinsky coefficient (Cs²), which is clipped to zero to prevent backscatter.

Related Work
Germano, M., Piomelli, U., Moin, P., & Cabot, W. H. (1991). A dynamic subgrid-scale eddy viscosity model. Physics of Fluids A, 3(7), 1760–1765.
Lilly, D. K. (1992). A proposed modification of the Germano subgrid-scale closure method. Physics of Fluids A, 4(3), 633–635.
Related to the existing ones CSmagorinskyModel and CWALEModel implementations in the same file.

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