Implement peer-to-peer communication between nodes

[devduart]

Summary

Build a simple P2P network so nodes can share blocks and synchronize blockchain state.

Tasks

• Define a list of known peers (IP + port)
• Add endpoint POST /receive-block to accept new blocks from peers
• On new block mined, broadcast to all peers
• Add /sync endpoint to compare chains and adopt the longest valid one
• Handle duplicate or invalid blocks gracefully

Optional

• Use WebSocket or HTTP long polling for real-time communication
• Add GET /peers to monitor network

Goal

Simulate a decentralized blockchain by allowing multiple instances to stay in sync.