Upgrade all code to Python ≥ 3.11 to support newer dependencies

[koustavchandra]

We should update all code bases to require Python 3.11 or newer. This will allow us to use later versions of several dependent packages.

For example:

• PyCBC now depends on numpy >= 2.
• Our current CI workflow tests with Python 3.10, which forces downgrades and overwrites dependency versions whenever we try to update requirements.txt.

By moving to Python ≥ 3.11 and updating CI accordingly, we can:

• Keep dependencies in sync with upstream projects.
• Avoid repetitive rewrites of requirements.txt.
• Ensure future compatibility with ongoing package releases.

[koustavchandra]

#53