Implement transaction propagation for wallets and nodes via Gossip P2P

[yago-123]

Add predicate validations. Example:

import (
    "context"
    "github.com/libp2p/go-libp2p-core/peer"
    gossipsub "github.com/libp2p/go-libp2p-pubsub"
)

func validateMessage(ctx context.Context, pid peer.ID, msg *gossipsub.Message) bool {
    // Example predicate: check message signature
    if !verifySignature(msg) {
        return false
    }

    // Example predicate: check message structure
    if !validateStructure(msg) {
        return false
    }

    // Example predicate: check content
    if !validateContent(msg) {
        return false
    }

    // All checks passed
    return true
}

func main() {
    // Create a new Gossipsub instance
    gs, err := gossipsub.NewGossipSub(context.Background(), host,
        gossipsub.WithMessageValidation(validateMessage))
    if err != nil {
        panic(err)
    }

    // Continue with Gossipsub setup...
}