Add support for Python 3.14

[seisman]

Python 3.14 has been released on 7 Oct 2025, changelog is at https://docs.python.org/3.14/whatsnew/3.14.html

Previous PR for Python 3.13 at #3490.

[weiji14]

If I understand correctly, most packages like pyogrio (used by geopandas) and rasterio (used by rioxarray) already have Python 3.14 packages on conda-forge, but there is a conflict on some Python 3.14 packages being built on libgdal-core=3.11 only, while rasterio is still stuck on libgdal-core=3.10 (xref conda-forge/rasterio-feedstock#332). So might still need to wait for rasterio/rasterio#3406