fix(lmxproxy): protect probe subscription from ReadAsync teardown, add instance configs

ReadAsync internally subscribes/unsubscribes the same ScanTime tag used
by the persistent probe, which was tearing down the probe subscription
and triggering false reconnects every ~5s. Guard UnsubscribeInternal and
stored subscription state so the probe tag is never removed by other
callers. Also removes DetailedHealthCheckService (redundant with the
persistent probe), adds per-instance config files (appsettings.v2.json,
appsettings.v2b.json) loaded via LMXPROXY_INSTANCE env var so deploys
no longer overwrite port settings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Status/StatusModels.cs

@@ -12,7 +12,6 @@ namespace ZB.MOM.WW.LmxProxy.Host.Status
         public SubscriptionStatus Subscriptions { get; set; } = new SubscriptionStatus();
         public PerformanceStatus Performance { get; set; } = new PerformanceStatus();
         public HealthInfo Health { get; set; } = new HealthInfo();
-        public HealthInfo? DetailedHealth { get; set; }
     }
 
     public class ConnectionStatus