No telemetry for deprecated-version usage to guide the v1 sunset

[nanaf6203-bit]

Context

version-header.interceptor/deprecation-warning.interceptor emit 299 warnings for v1, but nothing measures how many deprecated requests occur over time.

Problem

The team can't decide rationally when to sunset v1 without traffic data; docs (API_VERSIONING.md) promise a sunset policy that is currently guesswork. A lone signal would prevent breaking active integrations.

Proposed approach

Increment a api_version_requests_total{version} counter (metrics module) in the version interceptor/middleware, expose per-version usage in admin, and track deprecation-warning counts; document the gate criteria for sunset.

Acceptance criteria

• Per-version request metrics exist and are tested; dashboard shows usage.

[LEEN699300]

@LEEN699300 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi Maintainer, I’m ready to take ownership of this issue and see it through to completion. I’ll make sure the implementation is properly tested and meets the stated requirements. I’d appreciate the assignment.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @LEEN699300 to this issue.

[Medo99-olo]

@Medo99-olo has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Boss man, better gimme that thing

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Medo99-olo to this issue.

[drips-wave]

Congratulations, @Medo99-olo! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on September 30, 2026.

🧑‍💻 @Medo99-olo: 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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