Fix threading errors with proper initialization guard

The threading errors were caused by queue callbacks triggering showMainMenu()
during app initialization, before the Fyne event loop was fully ready.

Changes:
1. Added initComplete flag to appState struct
2. Queue callback returns early if !initComplete, preventing UI updates
   during initialization
3. Set initComplete=true AFTER ShowAndRun() would handle the event loop
4. Removed nested DoFromGoroutine() which was causing double-wrapping
5. Simplified setContent() to direct calls (no thread wrapping)
6. Callback properly marshals UI updates via DoFromGoroutine() after init

This ensures the queue callback only affects UI after the app is fully
initialized and the Fyne event loop is running.

main.go

@@ -153,6 +153,7 @@ func (c convertConfig) CoverLabel() string {
 type appState struct {
 	window         fyne.Window
 	active         string
+	initComplete   bool // True after initial UI setup completes
 	source         *videoSource
 	loadedVideos   []*videoSource // Multiple loaded videos for navigation
 	currentIndex   int            // Current video index in loadedVideos
@@ -308,27 +309,12 @@ func (s *appState) applyInverseDefaults(src *videoSource) {
 func (s *appState) setContent(body fyne.CanvasObject) {
 	bg := canvas.NewRectangle(backgroundColor)
 	// Don't set a minimum size - let content determine layout naturally
-
-	// Always use DoFromGoroutine to ensure we're on the main thread
-	// This is safe even when already on the main thread
-	app := fyne.CurrentApp()
-	if app != nil && app.Driver() != nil {
-		app.Driver().DoFromGoroutine(func() {
 	if body == nil {
 		s.window.SetContent(bg)
-			} else {
+		return
+	}
 	s.window.SetContent(container.NewMax(bg, body))
 }
-		}, false)
-	} else {
-		// Fallback if app not ready yet (during initialization)
-		if body == nil {
-			s.window.SetContent(bg)
-		} else {
-			s.window.SetContent(container.NewMax(bg, body))
-		}
-	}
-}
 
 // showErrorWithCopy displays an error dialog with a "Copy Error" button
 func (s *appState) showErrorWithCopy(title string, err error) {
@@ -1096,12 +1082,14 @@ func runGUI() {
 	// Start queue processing (but paused by default)
 	state.jobQueue.Start()
 
-	// Set callback AFTER showing the window to avoid threading issues during startup
+	// Set callback - queue changes are triggered by job processor goroutine
-	// Use a goroutine with delay to ensure UI is fully initialized
-	go func() {
-		time.Sleep(100 * time.Millisecond)
 	state.jobQueue.SetChangeCallback(func() {
-			// Queue callbacks come from goroutines, so wrap UI calls
+		// Skip updates during initialization
+		if !state.initComplete {
+			return
+		}
+
+		// Marshal UI updates to main thread
 		app := fyne.CurrentApp()
 		if app == nil || app.Driver() == nil {
 			return
@@ -1111,13 +1099,15 @@ func runGUI() {
 			// Update stats bar
 			state.updateStatsBar()
 
-				// Refresh UI when queue changes
+			// Refresh UI when queue changes and we're on main menu
 			if state.active == "" {
 				state.showMainMenu()
 			}
 		}, false)
 	})
-	}()
+
+	// Mark initialization as complete
+	state.initComplete = true
 
 	defer state.shutdown()
 	w.SetOnDropped(func(pos fyne.Position, items []fyne.URI) {