Enable alarm auto-subscribe on session open

Set MxGateway:Alarms with Enabled=true and the dev-rig subscription
expression \DESKTOP-6JL3KKO\Galaxy!DEV. Worker sessions now subscribe
their wnwrap alarm consumer on open; without this the QueryActiveAlarms
RPC returns an empty stream because no session is ever alarm-subscribed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/MxGateway.Server/appsettings.json

@@ -66,6 +66,12 @@
       "ConnectionString": "Server=localhost;Database=ZB;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;",
       "CommandTimeoutSeconds": 60,
       "DashboardRefreshIntervalSeconds": 30
+    },
+    "Alarms": {
+      "Enabled": true,
+      "SubscriptionExpression": "\\\\DESKTOP-6JL3KKO\\Galaxy!DEV",
+      "DefaultArea": "",
+      "RequireSubscribeOnOpen": false
     }
   }
 }