WebSocket real-time updates: faster polling + network events

- Reduce polling interval to 5 seconds for faster updates
- Add network update events (peer count changes)
- Include block type (PoS/PoW) in newBlock events
- Track connected WebSocket clients
- Emit networkUpdate when peer count changes

This enables real-time live feed on the explorer frontend.

node_modules/socket.io-adapter/dist/index.d.ts

@@ -0,0 +1,2 @@
+export { SocketId, PrivateSessionId, Room, BroadcastFlags, BroadcastOptions, Session, Adapter, SessionAwareAdapter, } from "./in-memory-adapter";
+export { ClusterAdapter, ClusterAdapterWithHeartbeat, ClusterAdapterOptions, ClusterMessage, ClusterResponse, MessageType, ServerId, Offset, } from "./cluster-adapter";