API versioning and deprecation policy

[codebestia]

Write docs/api-versioning.md. The backend serves unversioned REST routes and socket events consumed by a client that updates independently, and the codebase has already made breaking changes (removing sequenceNumber, moving the key-bundle route, requiring device on verify) with no written compatibility policy.

Acceptance criteria:

• States the current position honestly — routes are unversioned today — and defines the intended policy going forward
• Defines what counts as a breaking change for REST responses, socket event payloads and database-backed shapes
• Gives the deprecation procedure: how a field or event is marked, how long it is supported, and how clients are notified
• Documents the capability-negotiation mechanism as the existing precedent for shipping a protocol change without breaking older clients

[roobie001]

@roobie001 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hello maintainer, can i work on this issue please

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[Depo-dev]

@Depo-dev has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello team.

I’m Depodev, a software engineer with a strong background in building scalable systems and contributing to open-source projects. I’ve taken some time to go through the repository and understand the current implementation, and I’m clear on the issue, its context, and the expected outcome.

I’d love to work on this and take ownership of the fix. I’m confident I can cleanly resolve it while keeping everything aligned with the existing codebase and ensuring all criteria are met. Would appreciate being assigned to this issue.

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[drips-wave]

Congratulations, @Depo-dev! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

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[github-actions]

Closed by #592, merged into dev.

[drips-wave]

This issue has been completed by @Depo-dev as part of the Stellar Wave Program's 8th Wave 🥳

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