Fix memory leak in Oxidation model

[FilipovicLado]

Summary

• Fix shared_ptr cycle in lsOxidation.hpp: OxidationDeformation and OxidationMaskBending held strong references to each other, leaking the entire object pair on every LOCOS time step. Fixed by calling clearMaskVelocityField() in ~Oxidation() and at the start of solveFields to break the cycle before members are replaced or destroyed.
• Fix vtkIdList leak in lsWriteVisualizationMesh.hpp: vtkSmartPointer<vtkIdList> = vtkIdList::New() double-increments the refcount (once in New(), once in the vtkSmartPointer raw-pointer constructor), so the object is never freed. Changed to vtkSmartPointer<vtkIdList>::New() which uses TakeReference internally.
• Add LSan suppression file (tests/lsan_suppressions.txt): Suppresses known false positives — VTK 9.1 internal leak in vtkGeometryFilterHelper and OpenMP thread-pool initialization under musl libc.
• Wire suppression file into MultiSurfaceMesh and VisualizationMesh tests: Sets LSAN_OPTIONS automatically when VIENNALS_ENABLE_SANITIZER=ON so these VTK-dependent tests pass cleanly under sanitizer.