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/tests/ZB.MOM.WW.LmxProxy.Host.Tests/Status/StatusReportServiceTests.cs

@@ -52,8 +52,7 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Status
             var sm = new SubscriptionManager(client);
             var pm = new PerformanceMetrics();
             var health = new HealthCheckService(client, sm, pm);
-            var detailed = new DetailedHealthCheckService(client);
-            var svc = new StatusReportService(client, sm, pm, health, detailed);
+            var svc = new StatusReportService(client, sm, pm, health);
             return (svc, pm, sm);
         }