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_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+// +build windows
+
+package utils
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func PrepareBackgroundCommand(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
+}