Backend: Implement Webhook Listener for Stellar Ledger Events

[gabito1451]

Currently, the backend relies on manual status updates. We need a service that watches the Stellar ledger for contract events.

Acceptance Criteria:

• Use Stellar SDK's stream functionality to watch for EngagementInitializedEvent and ReclaimedEvent.
• Update database booking/payment status automatically when an event is detected.

[samjay8]

@samjay8 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hi Maintainer, can I work on this for you? ETA: 2 hours.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @samjay8 to this issue.

[drips-wave]

Congratulations, @samjay8! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @samjay8: 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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