New file src/physics_api.jl defining user-facing elasticity API:
- ElasticityPhysicsType (alias Elasticity) for problem configuration
- DirichletBC struct for prescribed displacements
- NeumannBC struct for surface tractions/pressures
- Physics{P} container for problem with elements and BCs
- Works with both CPU and GPU backends
- 183 lines with comprehensive examples
Jukka Aho