Refactor authentication challenge logic in HandleCount and HandleReq

- Updated the authentication challenge conditions in both HandleCount and HandleReq functions to check for the presence of an authenticated public key.
- Introduced the schnorr package to handle public key length validation.
- Bumped version to v0.25.7 to reflect these changes.

app/handle-req.go

@@ -52,7 +52,7 @@ func (l *Listener) HandleReq(msg []byte) (err error) {
 		},
 	)
 	// send a challenge to the client to auth if an ACL is active, auth is required, or AuthToWrite is enabled
-	if acl.Registry.Active.Load() != "none" || l.Config.AuthRequired || l.Config.AuthToWrite {
+	if len(l.authedPubkey.Load()) == 0 && (acl.Registry.Active.Load() != "none" || l.Config.AuthRequired || l.Config.AuthToWrite) {
 		if err = authenvelope.NewChallengeWith(l.challenge.Load()).
 			Write(l); chk.E(err) {
 			return