[Chore] Replace all base64 usages with faster pybase64 package

[Isotr0py]

Purpose

• Although Move to a faster base64 implementation #19984 introduced faster pybase64, there're still lots of legacy/new functions still use base64.
• This PR replaces all base64 usage with pybase64 and adds base64 to check_forbidden_imports.py similar to regex.

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[mergify]

Documentation preview: https://vllm--37290.org.readthedocs.build/en/37290/

[gemini-code-assist]

Code Review

This pull request replaces all usages of the standard base64 library with the faster pybase64 package. The changes are mostly correct and also include an update to the pre-commit hook to enforce this change. However, I found one critical issue in vllm/multimodal/media/audio.py where pybase64 is used without being imported, which will cause a NameError.

[mergify]

Hi @Isotr0py, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10