build: added support for uv

[mrava87]

This PR adds support for UV to PyProximal:

• update pyproject.toml
• add uv.lock*
• add targets in Makefile
• add build action in GA
• update readthedocs

• Currently created with the following set of commands:

uv venv --python 3.13
uv lock
uv sync --locked --all-extras --all-groups 

It also modernizes the overall tooling:

• move content of setup.cfg to pyproject.toml
• switch from black/flake8/isort to ruff
• add coverage support with upload to codacy (like pylops)

Finally, it contains various improvements to the documentation:

• add installation instructions for uv
• use sphinx-design to have tabs in installation instructions for conda/pip/uv
• added emojii in main section titles

[cako]

Looks really good! The website looks great. Left a few comments. For some improvements I'd consider:

• Use nox for local testing different Python versions
• Retire Makefile (doesn't work natively on Windows, but nox does)
• Default to uv, then conda, then pip.

Also, for the segmentation.py example to work, I need to crank up the maxiter to 30. Otherwise I get:

    r = _zeros._bisect(f, a, b, xtol, rtol, maxiter, args, full_output, disp)
RuntimeError: Failed to converge after 20 iterations.

[cako]

Suggest using typing_extensions>=4.0.0 since it's when they started using semantic versioning.

[cako]

This line complains when I run docs. Two suggestions: format this file with ruff and use raw string (r"\.py").

[cako]

Why is this file still required?