Add layout system and file selection logic

Introduce a new layout system for managing main window content and tabs. Integrate file selection and drag-and-drop functionality for adding files to the conversion list, with automatic tab switching to "Added Files". Refactor existing components to support these features.

internal/controller/main.go

@@ -22,8 +22,13 @@ func NewController(app application.AppContract) ControllerContract {
 	app.GetQueueService().AddListener(queueLayout)
 
 	return &controller{
-		app:    app,
-		window: window.NewMainWindow(fyneWindow, app.GetProgressBarService(), app.GetItemsToConvert(), queueLayout),
+		app: app,
+		window: window.NewMainWindow(
+			fyneWindow,
+			app.GetProgressBarService(),
+			app.GetItemsToConvert(),
+			queueLayout,
+		),
 	}
 }