Add enable/disable configuration for alarm tracking and historian integration

Both features now default to disabled and require explicit opt-in via
OpcUa.AlarmTrackingEnabled and Historian.Enabled in appsettings.json,
preventing errors in environments without a Historian database or alarm setup.

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

src/ZB.MOM.WW.LmxOpcUa.Host/appsettings.json

@@ -5,7 +5,8 @@
     "ServerName": "LmxOpcUa",
     "GalaxyName": "ZB",
     "MaxSessions": 100,
-    "SessionTimeoutMinutes": 30
+    "SessionTimeoutMinutes": 30,
+    "AlarmTrackingEnabled": false
   },
   "MxAccess": {
     "ClientName": "LmxOpcUa",
@@ -31,6 +32,7 @@
     "RefreshIntervalSeconds": 10
   },
   "Historian": {
+    "Enabled": false,
     "ConnectionString": "Server=localhost;Database=Runtime;Integrated Security=true;",
     "CommandTimeoutSeconds": 30,
     "MaxValuesPerRead": 10000