Update progress bar

[ASKabalan]

This pull request removes continuous optimization functionality from the codebase and deprecates related APIs in favor of an external package. It also updates documentation and project configuration to reflect this change, and introduces a new GitHub Actions workflow for notebook testing.

Deprecation and removal of continuous optimization:

• The optimize function and all related code (including parameter conditioning and progress tracking) have been removed from src/jax_grid_search/_optimizers.py. Instead, a stub remains that raises NotImplementedError and instructs users to use furax_cs.minimize from the furax-cs package.
• The condition function and default_desc_cb have been removed from the public API in src/jax_grid_search/__init__.py, and documentation now marks optimize as deprecated. [1] [2]
• Example and documentation references to continuous optimization and parameter conditioning have been removed from examples/README.md. [1] [2] [3] [4]
• Dependencies and type stubs related to continuous optimization (such as optax, optimistix, lineax, equinox, and jax-progress) have been removed from pyproject.toml. [1] [2]

Testing and documentation improvements:

• A new GitHub Actions workflow (.github/workflows/notebooks.yml) has been added to automatically execute all example notebooks across multiple Python versions and upload the outputs as artifacts.
• The main test workflow now includes Python 3.13 in its version matrix.
• The README.md has been updated to add a badge for the new notebooks workflow and clarify the naming of the tests badge.