[Testing] Add network and P2P layer tests

[qj0r9j0vc2]

Problem

Current test coverage:

• Total tests: 433
• Network/P2P tests: 0

No tests for:

• Message propagation
• Peer discovery
• Connection handling
• Network partitions
• Byzantine scenarios

Risk

• Network failures undetected until production
• Message loss handling untested
• Reconnection logic unverified

Required Tests

1. Basic peer connectivity
2. Message broadcast/receive
3. Connection drop and reconnect
4. Network partition simulation
5. Malformed message handling
6. Rate limiting behavior

Affected Crates

• crates/consensus (network layer)
• crates/data-chain (primary/worker communication)
• crates/node (peer management)