Bump golang.org/x/crypto to v0.56.0 to fix CVE-2026-78662

To fix CVE-2026-78662 published on Sep 02, 2026 and reported as a "High" vulnerability.

### CVE-2026-78662
"Previously, a channel registered in the mux's chanList is not usable until it is established. A malicious peer was able flood the channel's incomingRequests, deadlocking the entire connection. Now, we add an atomic established state, set when a channel becomes usable. Until such a time, handlePacket drops every packet other than the open confirmation/failure, without blocking and without tearing down the connection."

Locate the Go module dependency declaration and confirm where golang.org/x/crypto is pinned. Update it to v0.56.0, then run the repository's existing Go tests and verify that the vulnerable dependency version is no longer present.

Written by the indexing model from the issue text.