feat(configmanager): add ConnectionStrings editor with test connection support

Adds a new ConnectionStrings section to ConfigManager allowing users to manage
database connection strings with provider selection, connection testing, and
visual feedback for connection state.

NEW/src/Utils/JdeScoping.ConfigManager/Models/ConfigModel.cs

@@ -40,7 +40,7 @@ public class ConfigModel
     /// <summary>
     /// Gets or sets the connection strings for external data sources.
     /// </summary>
-    public Dictionary<string, string> ConnectionStrings { get; set; } = new();
+    public ConnectionStringsSection ConnectionStrings { get; set; } = new();
 
     /// <summary>
     /// Gets or sets the secure store configuration.