Feat/social controllers leaderboard opt out in

[Bigshmow]

Explanation

Adds optOutOfLeaderboard and optInToLeaderboard to SocialController and SocialService, with their corresponding messenger actions. @metamask/social-controllers previously had no way to opt a user out of (or back into) the Top Traders leaderboard; the mobile client needs these to remove/restore a user from the global, Clicker-backed leaderboard. Each method POSTs to the existing social-api endpoint (/leaderboard/opt-out, /leaderboard/opt-in) with the JWT already attached by SocialService, and resolves to void on the backend's 204. Purely additive — no existing methods, types, or behavior change.

References

• Related to TSA-830 - leaderboard opt-out: client flow + AUS persistence. Consumed by the MetaMask mobile client.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Purely additive API surface with tests; no changes to existing methods, state, or auth flow beyond new leaderboard preference calls.

Overview
Adds optOutOfLeaderboard and optInToLeaderboard to @metamask/social-controllers so clients (e.g. mobile) can remove or restore the signed-in user on the Top Traders / PnL leaderboard.

SocialService issues JWT-authenticated POST requests to /api/v1/leaderboard/opt-out and /api/v1/leaderboard/opt-in, treats success as 204, and surfaces failures via new LEADERBOARD_OPT_OUT_FAILED / LEADERBOARD_OPT_IN_FAILED messages. SocialController exposes the same operations as thin messenger delegates (no controller state changes). Messenger action types, package exports, changelog, and unit tests are updated accordingly.

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