Add Prometheus metrics endpoint to agent service

[robertocarlous]

Description

The agent service should expose Prometheus metrics for monitoring and alerting.

Current State

• No metrics endpoint
• Cannot monitor request latency
• Cannot track error rates

Expected Behavior

• Expose /metrics endpoint
• Track request duration histogram
• Track error rate counter
• Track OpenAI API usage
• Track Stellar RPC latency

Files Affected

• agent/src/
• agent/package.json (add prom-client dependency)

[Wiseman52]

@Wiseman52 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer, I’m confident I can take ownership of this task and deliver a well-tested solution that meets your expectations.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Wiseman52 to this issue.

[drips-wave]

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

🧑‍💻 @Ugooweb: 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.

Warning

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