[2.3] Tabulated EELS edges in the batched engine

[CSSFrancis]

EELSCLEdge is a GOS table lookup, not an analytic form, so it does not port like the other components.

Approach: interpolate the GOS table on-device (differentiable w.r.t. onset), and fit edge intensities through the linear/variable-projection path from [1.3] — the shapes are fixed and the amplitudes are linear, which is exactly the case VarPro handles well.

Parity against exspy's own edge model is the acceptance test.

Part of #60.

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Plan: RELEASE_0_3_0_PLAN.md

[CSSFrancis]

Delivered in 0.3.0, merged to main via #89.

3105585 — feat(spectroscopy): tabulated EELS edges, so EELS gets the GPU path too

Closing from the merge rather than automatically: the commits cite issues as (#63) rather than Closes #63, so GitHub linked none of them (#89 reported 0 closing references).