feat: ControlRenderer checks widget registry for custom widgets

Added registry lookup at top of renderWidget() before hardcoded switch.
Custom widgets registered via engine.registerWidget(type:factory) are
now rendered by the factory closure, enabling app-level extensions.

Sources/SwiftBricks/Renderer/ControlRenderer.swift

@@ -26,6 +26,16 @@ public struct ControlRenderer: View {
     func renderWidget(_ schema: ControlSchema) -> some View {
         let type = schema.widgettype
         
+        // 优先查找自定义注册的widget
+        if let factory = engine.getWidgetFactory(type: type) {
+            factory(schema, engine)
+        } else {
+        renderKnownWidget(schema, type: type)
+        }
+    }
+    
+    @ViewBuilder
+    func renderKnownWidget(_ schema: ControlSchema, type: String) -> some View {
         switch type {
         // 文本类
         case "Text":