ENH: Add JupyterLite CI/CD infrastructure

[natinew77-creator]

Tracking Issue: #13929

What does this implement/fix?
This PR integrates JupyterLite into the MNE-Python documentation build, allowing users to run tutorials interactively directly in their browser without a local Python environment.

Key technical implementations:

• Integrates jupyterlite-sphinx into the Sphinx-Gallery pipeline, automatically generating "Try in JupyterLite" buttons for tutorials and examples.
• Injects a hidden setup cell into the generated notebooks via conf.py to automatically handle Pyodide-specific browser quirks:
  • Installs mne and pyodide-http natively via micropip.
  • Patches Pyodide networking (pyodide_http.patch_all()) so MNE's pooch downloader can successfully fetch datasets from the browser.
  • Monkey-patches mne.viz.utils.plt_show to correctly render MNE's Matplotlib figures inline within the WebAssembly environment.

Additional information

• This represents the completion of the first major GSoC milestone.
• CircleCI will now automatically build the JupyterLite assets and provide a live preview link in the CI checks.
• Note on limitations: During testing, I identified two architectural edge cases for future discussion: browser RAM limitations when tutorials attempt to download massive (>1GB) datasets, and occasional PyPI vs. main branch version mismatches since JupyterLite currently pulls the stable MNE release.