[ MostroP2P/mostro ] feat: implement Phase 4 dev fee audit events via Nostr (#559)
* feat: implement Phase 4 dev fee audit events via Nostr
Add transparent audit trail for dev fee payments through Nostr events,
enabling third-party verification and analytics while maintaining user
privacy.
Changes:
- Add DEV_FEE_AUDIT_EVENT_KIND constant (38383) for audit events
https://github.com/MostroP2P/mostro/commit/12f9600c046992f87b14e3a8876242204d9aebe5