feat(routes-f): channel banner metadata

[davedumto]

Summary

Manage banner image metadata for a channel.

Requirements

• GET ?creator_id returns { banner_url, focal_point: { x, y } }
• PUT { creator_id, banner_url, focal_point? } updates
• Validate focal_point.x and y in [0,1]
• Tests cover update and validation

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.

[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??

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[drips-wave]

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

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[drips-wave]

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

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