Wire DCL to Instance Actors for OPC UA tag value flow

- Add TagValueUpdate/ConnectionQualityChanged handlers to InstanceActor
- InstanceActor subscribes to DCL on PreStart based on DataSourceReference
- DeploymentManagerActor creates DCL connections on deploy and passes DCL ref
- AkkaHostedService creates DCL Manager Actor for tag subscriptions
- Move CreateConnectionCommand to Commons for cross-project access
- Add ConnectionConfig to FlattenedConfiguration for deployment packaging

src/ScadaLink.Commons/Messages/DataConnection/CreateConnectionCommand.cs

@@ -0,0 +1,10 @@
+namespace ScadaLink.Commons.Messages.DataConnection;
+
+/// <summary>
+/// Command to create a new data connection actor for a specific protocol.
+/// Sent from DeploymentManagerActor to DCL Manager Actor.
+/// </summary>
+public record CreateConnectionCommand(
+    string ConnectionName,
+    string ProtocolType,
+    IDictionary<string, string> ConnectionDetails);

src/ScadaLink.Commons/Types/Flattening/FlattenedConfiguration.cs

@@ -17,6 +17,22 @@ public sealed record FlattenedConfiguration
     public IReadOnlyList<ResolvedAlarm> Alarms { get; init; } = [];
     public IReadOnlyList<ResolvedScript> Scripts { get; init; } = [];
     public DateTimeOffset GeneratedAtUtc { get; init; } = DateTimeOffset.UtcNow;
+
+    /// <summary>
+    /// Connection configurations keyed by connection name, each containing the
+    /// protocol-specific settings (e.g. OPC UA endpoint, publish interval).
+    /// Populated during flattening from the instance's connection bindings.
+    /// </summary>
+    public IReadOnlyDictionary<string, ConnectionConfig>? Connections { get; init; }
+}
+
+/// <summary>
+/// Connection configuration included in the flattened deployment package.
+/// </summary>
+public sealed record ConnectionConfig
+{
+    public string Protocol { get; init; } = string.Empty;
+    public string? ConfigurationJson { get; init; }
 }
 
 /// <summary>