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/LmxProxyService.cs

@@ -30,7 +30,6 @@ namespace ZB.MOM.WW.LmxProxy.Host
         private ApiKeyService? _apiKeyService;
         private PerformanceMetrics? _performanceMetrics;
         private HealthCheckService? _healthCheckService;
-        private DetailedHealthCheckService? _detailedHealthCheckService;
         private StatusReportService? _statusReportService;
         private StatusWebServer? _statusWebServer;
         private Server? _grpcServer;
@@ -119,13 +118,11 @@ namespace ZB.MOM.WW.LmxProxy.Host
 
                 // 10. Create health check services
                 _healthCheckService = new HealthCheckService(_mxAccessClient, _subscriptionManager, _performanceMetrics);
-                _detailedHealthCheckService = new DetailedHealthCheckService(
-                    _mxAccessClient, _config.HealthCheck.TestTagAddress);
 
                 // 11. Create status report service
                 _statusReportService = new StatusReportService(
                     _mxAccessClient, _subscriptionManager, _performanceMetrics,
-                    _healthCheckService, _detailedHealthCheckService);
+                    _healthCheckService);
 
                 // 12. Start status web server
                 _statusWebServer = new StatusWebServer(_config.WebServer, _statusReportService);