Add account and team settings to the OpenAPI and Fern specs

[jspaetzel]

Summary

• Publish the v3 account and team settings endpoints, including an optional account or team id at the end of the path.
• Name team lock modes organization_admins, team_admins, and members.
• Add SDK examples and the SEO copy used by the generated docs spec.

Generated from the Sign settings branch: https://github.com/dropbox-internal/sign/pull/28857

Test plan

• Confirm ./build output matches this commit
• Review the four settings operations and TeamSettingLock in the generated spec
• Hold the docs publish until the API and public SDKs are released

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