Add structured keeper events and an inspectable health snapshot

[karagozemin]

Context

keeper:watch emits human-only console strings, making production alerting and liveness inspection difficult.

Scope

Add typed lifecycle events, JSON logging, and a lightweight optional health endpoint while retaining readable logs.

Acceptance criteria

• Events cover tick start/end, reveal open, reveal/skip, clear, settle, void, retry, and error.
• Support text and newline-delimited JSON modes.
• JSON includes timestamp, network, contract, round, event, status, and actionable error metadata.
• Track start time, last completed tick/action, active rounds, and recent error summary.
• Expose an optional localhost-by-default health/readiness endpoint.
• Never expose secret keys, signed XDR, or sensitive env values.
• Test serialization, redaction, and readiness transitions.
• Document configuration and sample output.

Out of scope

Hosted monitoring or a metrics database.

Verification

Demonstrate text, JSON, and health output in the PR.

[Samuel-21-eng]

@Samuel-21-eng has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I've read through the description and I'm confident that I can get this done with the necessary fixes and improvements

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Samuel-21-eng to this issue.

[drips-wave]

Congratulations, @Samuel-21-eng! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Samuel-21-eng: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

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