FEAT: Libp2p P2P Sync

[github-actions]

🎯 Objective

Implement the core functionality for the Libp2p P2P Sync feature.

📦 Crate

$(@{id=libp2p-sync; name=Libp2p P2P Sync; phase=4; crate=synapse-infra; passes=False; tests=System.Object[]; last_updated=}.crate)

📚 Description from features.json

Libp2p P2P Sync

This task was automatically generated by the Planner Agent based on the project's feature manifest. The goal is to implement this feature and ensure all related tests pass.