fix(bytes32): use memcpy for std::hash to fix macOS build

[alienx5499]

This Pull Request fixes/closes #188.

It changes the following:

• Fix std::hash<Bytes32> in src/Bytes32.h: remove the ill-formed cast from size_t* to uint64_t* (fails on Apple Clang / arm64 where size_t and uint64_t are distinct typedefs).
• Hash the 32-byte buffer by copying into uint64_t words[4] with memcpy, then XOR the four lanes—same hash shape as before, without pointer type punning.
• Include <cstdint> so uint64_t is explicit in the header.

Testing

• make setup-golpe && make -j4 (with dependencies available per README / your environment, e.g. Homebrew CPATH / LIBRARY_PATH on macOS)
• make src/Decompressor.o (quick check that Bytes32.h compiles on the inclusion path used by the build)

[hoytech]

Makes sense, to ensure there's no unaligned access on CPUs where that matters. Probably the compiler can avoid the memcpy when not necessary. Thanks!