feat: implement ETL pipeline redesign and ConfigManager improvements

- Add pipeline registry with JSON-based configuration and hot-reload support
- Implement manual sync request feature with API, client UI, and database
- Improve ConfigManager: connection string dropdown in pipeline editor,
  step delete/reorder functionality, and fix JSON parsing for ConnectionStrings

NEW/src/JdeScoping.DataSync/Configuration/SourceElement.cs

@@ -0,0 +1,27 @@
+namespace JdeScoping.DataSync.Configuration;
+
+/// <summary>
+/// Configuration for the pipeline data source.
+/// </summary>
+public class SourceElement
+{
+    /// <summary>
+    /// Connection identifier (jde, cms, giw, lotfinder).
+    /// </summary>
+    public string Connection { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Query for incremental syncs (daily/hourly).
+    /// </summary>
+    public string Query { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Query for mass sync. Falls back to Query if not specified.
+    /// </summary>
+    public string? MassQuery { get; set; }
+
+    /// <summary>
+    /// Query parameters with format and source configuration.
+    /// </summary>
+    public Dictionary<string, ParameterElement> Parameters { get; set; } = new();
+}