feat(etl): add core ETL pipeline interfaces

Add the four core interfaces for the ETL pipeline:
- IImportSource: defines data sources for reading
- IDataTransformer: defines data transformation layer
- IImportDestination: defines data write destinations
- IScriptRunner: defines script execution capability

NEW/src/JdeScoping.DataSync/Etl/Contracts/IScriptRunner.cs

@@ -0,0 +1,18 @@
+namespace JdeScoping.DataSync.Etl.Contracts;
+
+/// <summary>
+/// Defines a runner that can execute scripts as part of the ETL process.
+/// </summary>
+public interface IScriptRunner
+{
+    /// <summary>
+    /// Executes the script asynchronously.
+    /// </summary>
+    /// <param name="cancellationToken">Token to cancel the operation.</param>
+    Task ExecuteAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the name of this script for logging and identification.
+    /// </summary>
+    string ScriptName { get; }
+}