`mat3x4_cast(tdualquat<T, Q> const& x)` fails to compile

This function uses `length2(qua)` defined in `quaternion.hpp` which was not included in `dual_quaternion.inl` therefore it tries to use generic `genType length2(genType)` resulting in missing `operator/(qua, qua)` compilation error.

Reproduceable in Clang 20 and GCC 15

Fix: include `quaternion.hpp` in `dual_quaternion.inl`

Should I open PR for this or is it already solved somewhere?