[BUG] Preserve input dtype in shift_scale_invariant zero-padding

[Jorge-Polanco-Roque]

Reference Issues/PRs

Fixes #3722.

What does this implement/fix? Explain your changes.

shift_scale_invariant_distance (and KSpectralCentroid, which uses it) raised a numba TypingError on float32 input: the zero-padding in the shift branches of _univariate_shift_scale_invariant_distance was built with an untyped np.zeros, which defaults to float64, so shifted_y could not unify across the branches (float32 from y, float64 from the padded ones). Passing dtype=y.dtype to both zero-padding branches keeps everything at the input dtype.

Does your contribution introduce a new dependency? If yes, which one?

No.

Any other comments?

Verified shift_scale_invariant_distance and KSpectralCentroid now fit/run on float32, matching the float64 result.

PR checklist

For all contributions

• The PR title starts with [BUG].
• I've added a test (test_shift_scale_invariant_distance_float32); verified it fails without the fix. ruff is green.
• I'll add myself via the @all-contributors bot after merge.

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[Jorge-Polanco-Roque]

The run-notebook-examples failure is unrelated to this change: it's examples/visualisation/plotting_estimators.ipynb raising ImportError: You must install graphviz ... for plot_model to work (graphviz missing in the CI environment). This PR only touches the shift_scale_invariant distance; examples/distances/distances.ipynb and plotting_distances.ipynb pass.