feat: wire SQLite replication between site nodes and fix ConfigurationDatabase tests

Add SiteReplicationActor (runs on every site node) to replicate deployed
configs and store-and-forward buffer operations to the standby peer via
cluster member discovery and fire-and-forget Tell. Wire ReplicationService
handler and pass replication actor to DeploymentManagerActor singleton.

Fix 5 pre-existing ConfigurationDatabase test failures: RowVersion NOT NULL
on SQLite, stale migration name assertion, and seed data count mismatch.

src/ScadaLink.Commons/Interfaces/Services/IExternalSystemClient.cs

@@ -1,3 +1,5 @@
+using ScadaLink.Commons.Types;
+
 namespace ScadaLink.Commons.Interfaces.Services;
 
 /// <summary>
@@ -34,4 +36,27 @@ public record ExternalCallResult(
     bool Success,
     string? ResponseJson,
     string? ErrorMessage,
-    bool WasBuffered = false);
+    bool WasBuffered = false)
+{
+    private dynamic? _response;
+    private bool _responseParsed;
+
+    /// <summary>
+    /// Parsed response as a dynamic object. Returns null if ResponseJson is null or empty.
+    /// Access properties directly: result.Response.result, result.Response.items[0].name, etc.
+    /// </summary>
+    public dynamic? Response
+    {
+        get
+        {
+            if (!_responseParsed)
+            {
+                _response = string.IsNullOrEmpty(ResponseJson)
+                    ? null
+                    : new DynamicJsonElement(System.Text.Json.JsonDocument.Parse(ResponseJson).RootElement);
+                _responseParsed = true;
+            }
+            return _response;
+        }
+    }
+}

src/ScadaLink.Commons/Messages/Management/ExternalSystemCommands.cs

@@ -5,3 +5,10 @@ public record GetExternalSystemCommand(int ExternalSystemId);
 public record CreateExternalSystemCommand(string Name, string EndpointUrl, string AuthType, string? AuthConfiguration);
 public record UpdateExternalSystemCommand(int ExternalSystemId, string Name, string EndpointUrl, string AuthType, string? AuthConfiguration);
 public record DeleteExternalSystemCommand(int ExternalSystemId);
+
+// External System Methods
+public record ListExternalSystemMethodsCommand(int ExternalSystemId);
+public record GetExternalSystemMethodCommand(int MethodId);
+public record CreateExternalSystemMethodCommand(int ExternalSystemId, string Name, string HttpMethod, string Path, string? ParameterDefinitions = null, string? ReturnDefinition = null);
+public record UpdateExternalSystemMethodCommand(int MethodId, string? Name = null, string? HttpMethod = null, string? Path = null, string? ParameterDefinitions = null, string? ReturnDefinition = null);
+public record DeleteExternalSystemMethodCommand(int MethodId);

src/ScadaLink.Commons/Messages/Management/TemplateCommands.cs

@@ -14,8 +14,8 @@ public record DeleteTemplateAttributeCommand(int AttributeId);
 public record AddTemplateAlarmCommand(int TemplateId, string Name, string TriggerType, int PriorityLevel, string? Description, string? TriggerConfiguration, bool IsLocked);
 public record UpdateTemplateAlarmCommand(int AlarmId, string Name, string TriggerType, int PriorityLevel, string? Description, string? TriggerConfiguration, bool IsLocked);
 public record DeleteTemplateAlarmCommand(int AlarmId);
-public record AddTemplateScriptCommand(int TemplateId, string Name, string Code, string? TriggerType, string? TriggerConfiguration, bool IsLocked);
-public record UpdateTemplateScriptCommand(int ScriptId, string Name, string Code, string? TriggerType, string? TriggerConfiguration, bool IsLocked);
+public record AddTemplateScriptCommand(int TemplateId, string Name, string Code, string? TriggerType, string? TriggerConfiguration, bool IsLocked, string? ParameterDefinitions = null, string? ReturnDefinition = null);
+public record UpdateTemplateScriptCommand(int ScriptId, string Name, string Code, string? TriggerType, string? TriggerConfiguration, bool IsLocked, string? ParameterDefinitions = null, string? ReturnDefinition = null);
 public record DeleteTemplateScriptCommand(int ScriptId);
 public record AddTemplateCompositionCommand(int TemplateId, string InstanceName, int ComposedTemplateId);
 public record DeleteTemplateCompositionCommand(int CompositionId);

src/ScadaLink.Commons/Types/DynamicJsonElement.cs

@@ -0,0 +1,92 @@
+using System.Dynamic;
+using System.Text.Json;
+
+namespace ScadaLink.Commons.Types;
+
+/// <summary>
+/// Wraps a JsonElement as a dynamic object for convenient property access in scripts.
+/// Supports property access (obj.name), indexing (obj.items[0]), and ToString().
+/// </summary>
+public class DynamicJsonElement : DynamicObject
+{
+    private readonly JsonElement _element;
+
+    public DynamicJsonElement(JsonElement element)
+    {
+        _element = element;
+    }
+
+    public override bool TryGetMember(GetMemberBinder binder, out object? result)
+    {
+        if (_element.ValueKind == JsonValueKind.Object &&
+            _element.TryGetProperty(binder.Name, out var prop))
+        {
+            result = Wrap(prop);
+            return true;
+        }
+        result = null;
+        return false;
+    }
+
+    public override bool TryGetIndex(GetIndexBinder binder, object[] indexes, out object? result)
+    {
+        if (_element.ValueKind == JsonValueKind.Array &&
+            indexes.Length == 1 && indexes[0] is int index)
+        {
+            var arrayLength = _element.GetArrayLength();
+            if (index >= 0 && index < arrayLength)
+            {
+                result = Wrap(_element[index]);
+                return true;
+            }
+        }
+        result = null;
+        return false;
+    }
+
+    public override bool TryConvert(ConvertBinder binder, out object? result)
+    {
+        result = ConvertTo(binder.Type);
+        return result != null || binder.Type == typeof(object);
+    }
+
+    public override string ToString()
+    {
+        return _element.ValueKind switch
+        {
+            JsonValueKind.String => _element.GetString() ?? "",
+            JsonValueKind.Number => _element.GetRawText(),
+            JsonValueKind.True => "true",
+            JsonValueKind.False => "false",
+            JsonValueKind.Null => "",
+            _ => _element.GetRawText()
+        };
+    }
+
+    private object? ConvertTo(Type type)
+    {
+        if (type == typeof(string)) return ToString();
+        if (type == typeof(int) && _element.ValueKind == JsonValueKind.Number) return _element.GetInt32();
+        if (type == typeof(long) && _element.ValueKind == JsonValueKind.Number) return _element.GetInt64();
+        if (type == typeof(double) && _element.ValueKind == JsonValueKind.Number) return _element.GetDouble();
+        if (type == typeof(decimal) && _element.ValueKind == JsonValueKind.Number) return _element.GetDecimal();
+        if (type == typeof(bool) && (_element.ValueKind == JsonValueKind.True || _element.ValueKind == JsonValueKind.False))
+            return _element.GetBoolean();
+        return null;
+    }
+
+    private static object? Wrap(JsonElement element)
+    {
+        return element.ValueKind switch
+        {
+            JsonValueKind.Object => new DynamicJsonElement(element),
+            JsonValueKind.Array => new DynamicJsonElement(element),
+            JsonValueKind.String => element.GetString(),
+            JsonValueKind.Number => element.TryGetInt64(out var l) ? l : element.GetDouble(),
+            JsonValueKind.True => true,
+            JsonValueKind.False => false,
+            JsonValueKind.Null => null,
+            _ => element.GetRawText()
+        };
+    }
+}

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

@@ -60,5 +60,6 @@ public enum ValidationCategory
     ReturnTypeMismatch,
     TriggerOperandType,
     OnTriggerScriptNotFound,
-    CrossCallViolation
+    CrossCallViolation,
+    MissingMetadata
 }