Add FFmpeg utilities configuration UI and automated downloading

Introduce a new UI for configuring FFmpeg, FFprobe, and FFplay paths with file selection and error handling. Add platform-specific logic for downloading and extracting FFmpeg binaries directly within the application, improving user experience.

internal/ffmpeg/download/gui/download_anyos.go

@@ -0,0 +1,14 @@
+//go:build !windows && !linux
+// +build !windows,!linux
+
+package gui
+
+import (
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/canvas"
+	"fyne.io/fyne/v2/widget"
+)
+
+func DownloadFFmpeg(donwloadFFmpeg func(progressBar *widget.ProgressBar, progressMessage *canvas.Text) error) fyne.CanvasObject {
+	return container.NewVBox()
+}