- Add Server-Sent Events endpoint at GET /api/mesh/gate/stream that
broadcasts ALL gate events to connected frontends (privacy: no
per-gate subscriptions, clients filter locally)
- Hook SSE broadcast into all gate event entry points: local append,
peer push receiver, and pull loop
- Reduce push/pull intervals from 30s to 10s for faster relay sync
- Add useGateSSE hook for frontend EventSource integration
- GateView + MeshChat use SSE for instant refresh, polling demoted
to 30s fallback
Latency: same-node instant, cross-node ~10s avg (was ~34s)