[Feature Request] Self-service toggle for individual extra usage opt-in

Bug Description
Title: Allow individual users to self-manage the "extra usage" opt-in toggle

Body:

I'd like to be able to enable and disable extra usage on my own account without
going through an admin.

My use case: I normally keep extra usage off as a personal safeguard against
accidentally burning through paid quota. If I exhaust my included quota and
genuinely need to keep working, I'd go enable it myself — then turn it off again
once I'm done or can wait for the quota to replenish.

This is purely about giving me control over my own spending behavior. I'm not
trying to bypass org policy — I just want the toggle to be in my hands, not require
an admin round-trip every time.

Request: Expose the extra usage toggle as a self-service control for individual
users, with an optional org-level policy to allow or restrict it per user/team.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.170
• Feedback ID: d225907a-73c6-4985-a234-070ad57d8367

Errors

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