feat(license): show Instance ID with copy on settings + ProGate

Always return machine fingerprint instanceId from license status for
offline LICOFF- binding. Shared InstanceIdRow (zh/en) above activate.

backend/services/license.go

@@ -306,14 +306,17 @@ func deriveInvalidReason(lic *models.License) string {
 
 // LicenseStatusPayload 给前端：始终带回库存证的 sanitized + 是否有效 Pro。
 // 无效时带 invalidReason（expired|over_instance|revoked），且不清 LicenseKey。
+// instanceId 始终返回本机指纹（DATA_DIR/instance.id），供离线 LICOFF- 绑码展示。
 func LicenseStatusPayload() (map[string]interface{}, bool) {
 	RefreshOpsxLicenseIfDue()
 	current := CurrentLicense()
 	stored := StoredLicense()
+	instanceID := GetOrCreateInstanceID()
 	if stored == nil {
-		return map[string]interface{}{"plan": "free"}, false
+		return map[string]interface{}{"plan": "free", "instanceId": instanceID}, false
 	}
 	out := stored.Sanitized()
+	out["instanceId"] = instanceID
 	if current != nil {
 		delete(out, "invalidReason")
 		return out, true