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.

• Update the branch protection rules after merging this PR.

[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

[seisman]

All workflows now pass with Python 3.14, except the "Static Type Checks" workflow, which fails because rasterio 1.4.3 doesn't provide a Python 3.14 binary wheel on PyPI.

But, it's likely we don't have to install optional dependencies when running mypy.

Edit: I've removed all optional dependencies in c73aac8 and the "Static Type Checks" workflow now passed. Don't remember why I added them in PR #2808.

[weiji14]

Awesome, good that we don't need to wait for rasterio anymore!