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-parser/build/cjs/is-binary.d.ts

@@ -0,0 +1,7 @@
+/**
+ * Returns true if obj is a Buffer, an ArrayBuffer, a Blob or a File.
+ *
+ * @private
+ */
+export declare function isBinary(obj: any): boolean;
+export declare function hasBinary(obj: any, toJSON?: boolean): boolean;