Affine quantization

FloatLib's RealAffineQuantizer supplies a real-valued scale, bounded integer codes, and a caller-chosen rounding rule. Its AffineQuantizer supplies executable rational nearest-even quantization; the Flocq adapter proves agreement with the real specification.

TorchLean adds shape-polymorphic tensor operations in NN.Spec.Quantization. Scalar definitions and rounding proofs stay in FloatLib so tensor clients use the same grids and error bounds.

The equations follow Jacob et al., "Quantization and Training of Neural Networks for Efficient Integer-Arithmetic-Only Inference," CVPR 2018, doi:10.1109/CVPR.2018.00286.