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/utils/prepare_background_command.go

@@ -0,0 +1,12 @@
+//go:build !windows
+// +build !windows
+
+package utils
+
+import (
+	"os/exec"
+)
+
+func PrepareBackgroundCommand(cmd *exec.Cmd) {
+
+}