fix: handle mixed JSON types in data connection config deserialization

DeploymentManagerActor deserialized connection config JSON as
Dictionary<string, string>, which silently failed on non-string values
like {"publishInterval":1000}. The OPC UA adapter then fell back to
localhost:4840 (unreachable in Docker). Now uses JsonDocument to handle
any JSON value type. OPC PLC Simulator connects successfully.

src/ScadaLink.SiteRuntime/Actors/DeploymentManagerActor.cs

@@ -375,8 +375,12 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
                 {
                     try
                     {
-                        var parsed = System.Text.Json.JsonSerializer.Deserialize<Dictionary<string, string>>(connConfig.ConfigurationJson);
+                        // Parse as JsonElement to handle mixed value types (string, int, bool)
-                        if (parsed != null) connectionDetails = parsed;
+                        using var doc = System.Text.Json.JsonDocument.Parse(connConfig.ConfigurationJson);
+                        foreach (var prop in doc.RootElement.EnumerateObject())
+                        {
+                            connectionDetails[prop.Name] = prop.Value.ToString();
+                        }
                     }
                     catch { /* Ignore parse errors */ }
                 }