Translate api.url configuration docs to es, fr, zh

[mintlify]

Summary

• Added translations for the new api.url configuration option to Spanish, French, and Chinese versions of the API playground overview page
• This mirrors the changes from PR Add api.url configuration documentation #4040 which added the url ResponseField documentation

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Note

Low Risk
Documentation-only updates adding translated content; no runtime or API behavior changes.

Overview
Adds localized documentation for the new api.url configuration option (displaying full base URLs in endpoint headers) to the Spanish, French, and Chinese api-playground/overview.mdx pages.

Also makes a small French copy edit to use consistent apostrophes in the examples description.

^{Written by Cursor Bugbot for commit 965bace. This will update automatically on new commits. Configure here.}