Translate variables property docs to es/fr/zh

[mintlify]

Summary

• Added variables ResponseField section to es/, fr/, and zh/ translations of organize/settings.mdx
• Added variables examples to JSON code blocks in all three translated files

Translation of changes from PR #3872.

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Note

Low Risk
Documentation-only updates to localized settings.mdx pages; no runtime logic or configuration parsing changes.

Overview
Adds documentation for the docs.json variables object to the Spanish, French, and Chinese organize/settings.mdx translations, including guidance on {{variableName}} substitution, required definitions, allowed key formats, and XSS sanitization.

Updates the JSON examples in each translation to include a sample variables block, and makes a small wording/typography tweak in the French tab title (and translates the Spanish “Structure” heading to “Estructura”).

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