feat: add any() and all() logical reduction methods - #29

This PR adds any() and all() boolean reduction methods to NDArray

Motivation and Context

These were the last missing basic reduction operations. any() and all() are fundamental for boolean array evaluation — checking conditions, validating constraints, and filtering logic. They were tracked in SPEC.md as unimplemented items 8.2.1 and 8.2.2.

What's Changed

• Two new Rust FFI modules (any.rs, all.rs) with scalar and axis reduction functions
• any(?int $axis = null, bool $keepdims = false): bool|NDArray — tests whether any element is true
• all(?int $axis = null, bool $keepdims = false): bool|NDArray — tests whether all elements are true
• 31 test cases covering scalar, axis, keepdims, float, int, bool data, 3D arrays
• Updated SPEC.md, statistics API reference, and NumPy migration guide

Breaking Changes

None.