[medium] Deprecate legacy /v0 verification endpoints

[davedumto]

Summary

The legacy /v0 verification endpoints are superseded by newer versioned routes but remain active with no deprecation signal.

Requirements

• Add a deprecation warning header to /v0 responses
• Log usage of /v0 endpoints to measure remaining traffic
• Document a removal timeline in docs/decisions.md
• Add a test verifying the deprecation header is present

[kathy-ai-art]

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

Hello maintainer, I'd be delighted to work on this. PLease assign

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[Kappa16]

@Kappa16 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

please maintainer assign this issue to me ..expect pr as soon as possible please

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[noevidence1017]

@noevidence1017 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi! This looks like an interesting issue, and I'd love to contribute. I've taken the time to understand the requirements and am confident I can deliver a high-quality solution. Looking forward to contributing if given the chance!

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Congratulations, @noevidence1017! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

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