Modify script to add python SDK SHA from python 3.14 onwards

[Shi1810]

This PR adds fetch_python_sha256(version) which:

• First tries the python.org release file API (sha256_sum field)
• If the API field is empty (common for newly published releases), falls back to downloading the .tar.xz tarball and computing SHA256 locally
• Returns uppercase hex string to match existing convention