[Enhancement]: Add support for Python 3.14 in local repo

[tomvothecoder]

Is your feature request related to a problem?

Python 3.14.0 (stable) releases on 10/07/2025 (https://peps.python.org/pep-0745/#schedule).

Describe the solution you'd like

1. Add 3.14 GH Actions Python test matrix
2. Remove <3.14 constraint in conda environment yaml files
3. Add 3.14 to pyproject.toml

Describe alternatives you've considered

No response

Additional context

No response

[tomvothecoder]

Note, I did not constrain the condo-forge recipe to python < 3.14 with the release of xcdat=0.10.1.

This means xcdat is compatible with Python 3.14; however, xesmf sub-dependencies including numba/llvmlite are not yet compatible with Python 3.14 (refer to #813).