Fix decentralized clients connection issue

[ahzero7d1]

Solves issue: #1109

We add two additional messages, ConnectionsReady and StartWeightSharing, exchanged between server and clients. The usage is as follows.

• Clients send ConnectionsReady message to the server after establishing all connections with peers.
• Once the server receives ConnectionsReady from all participants in the round, it sends StartWeightSharing message to participants.
• Clients proceed to exchange weight updates only after receiving StartWeightSharing from the server.

With this approach, all peers are guaranteed to complete their connection setup before weight updates are shared, preventing missed updates.