br: correct the store speed #20973

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• This PR is translated from: br: correct the store speed docs-cn#20973
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[gemini-code-assist]

Code Review

This pull request contains a mix of unrelated changes. The title suggests a correction to the BR store speed, which is reflected in br/br-snapshot-guide.md. However, the PR also introduces a very large set of new Python scripts for a documentation translation workflow, changes a repository owner in a script to a personal username, and removes some feature documentation from system-variables.md. It's highly recommended to split these unrelated changes into separate pull requests for clarity and easier review. My feedback focuses on the specific changes in the diff.

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