feat(routes-f): stream handoff endpoint

[davedumto]

Summary

Hand off control of a live stream from one host to another mid-stream.

Requirements

• POST { stream_id, from_user_id, to_user_id } -> { handed_off_at }
• Validate to_user_id is in the hosts list
• Log handoff history
• GET ?stream_id returns handoff log
• Tests cover successful handoff and unauthorized requester

Scope Constraint - READ BEFORE STARTING

All files for this task must live inside app/api/routes-f/. This includes the route handler, helpers/utilities, types, and tests. Do NOT modify, import from, or add files to lib/, utils/, types/, components/, or anywhere else outside app/api/routes-f/. If you need shared logic, duplicate it inside your subfolder. Keeping everything scoped to this folder is intentional - it keeps these tasks independent and mergeable in any order.

Product Context

StreamFi is a blockchain-powered live streaming platform. Streamers broadcast via Mux, viewers tip in Stellar XLM/USDC, creators have stream privacy modes (public/unlisted/subscribers-only). Build these issues as practice implementations - use realistic data shapes that match the platform domain, but do not import from the real app code.

[numdinkushi]

@numdinkushi has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I would like to work on this issue

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[IbrahimIjai]

@IbrahimIjai has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Can I work on thhis issue sir??

ℹ️ Repo Maintainers: To accept this application, review their application or assign @IbrahimIjai to this issue.

[drips-wave]

Congratulations, @IbrahimIjai! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @IbrahimIjai: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @IbrahimIjai as part of the Stellar Wave Program's 6th Wave 🥳

😎 @IbrahimIjai: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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