Feat(go): add Signer interface + License Server for multi-customer deployments

server/go/licensing/noop.go

@@ -0,0 +1,18 @@
+package licensing
+
+// NoOpSigner returns an empty signature. Used when neither YAMA_SIGN_PASSWORD
+// nor YAMA_LICENSE_SERVER is set — operator hasn't configured licensing at
+// all (free-tier mode). Device list keeps working; the client's private
+// library refuses to start screen/file features when it sees a zeroed
+// Signature[64] field in CMD_MASTERSETTING.
+type NoOpSigner struct{}
+
+func NewNoOp() *NoOpSigner { return &NoOpSigner{} }
+
+func (n *NoOpSigner) Sign(startTime, clientID string) (string, error) {
+	return "", nil
+}
+
+func (n *NoOpSigner) Mode() string { return "noop" }
+
+func (n *NoOpSigner) Close() error { return nil }