Add tetrahedral discrete SE3 group

[franciscoeacosta]

Summary

• implement the finite group $\mathbb{Z}_n^3 \rtimes A_4$
• construct lazy induced irreducible representations from translation-character orbits and little groups
• add focused tests for group laws, representation completeness, Fourier transforms, and conjugate pairs

Test plan

• pytest test/test_discrete_se3_a4_irreps.py -q
• ruff check on changed Python files
• ruff format --check on changed Python files

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