feat(license): dual-path opsx-licence client alongside HMAC

Wire LIC-/LICOFF- activate/verify/heartbeat to licence.rlwj.cn/api,
keep legacy HMAC accepted with deprecation banner, add instance_id
fingerprint and licensing docs (product lokistack still needs admin create).

backend/controllers/system.go

@@ -45,6 +45,7 @@ func (ctrl *SystemController) Health(c *gin.Context) {
 
 // LicenseStatus 当前授权(登录即可见:前端按 plan 显示锁/引导)
 func (ctrl *SystemController) LicenseStatus(c *gin.Context) {
+	services.RefreshOpsxLicenseIfDue()
 	lic := services.CurrentLicense()
 	utils.Success(c, gin.H{
 		"license":  lic.Sanitized(),