Add Notification Delivery Metrics API

[Abd-Standard]

Description

Expose delivery statistics through an API endpoint for monitoring notification performance.

Acceptance Criteria
Metrics endpoint is available.
Response includes delivery statistics.
Endpoint is documented.

[iredis]

@iredis has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I’d love to work on this issue because it’s a great opportunity to contribute, improve my skills, and deliver a meaningful solution while learning from the project.

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

[kitWarse]

@kitWarse has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello pls can I work on this

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

[drips-wave]

Congratulations, @kitWarse! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @kitWarse: 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.

🌊 Happy Wave 🌊

[drips-wave]

This issue has been removed from the Stellar Wave Program by the repository maintainers.

@kitWarse, you have been unassigned from this issue. If you have any questions, please reach out to the repo maintainers.