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/ffplay.go

@@ -1,19 +1,52 @@
 package ffmpeg
 
+import (
+	"errors"
+	"fyne.io/fyne/v2/lang"
+	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/internal/utils"
+	"os/exec"
+	"strings"
+)
+
 type FFplayContract interface {
-	SetPath(path string)
+	GetPath() string
 }
 
 type ffplay struct {
 	path string
 }
 
-func newFFplay(path string) FFplayContract {
+func newFFplay(path string) (FFplayContract, error) {
+	if path == "" {
+		return nil, errors.New(lang.L("errorFFplay"))
+	}
+
+	isCheck, err := checkFFplayPath(path)
+	if err != nil {
+		return nil, err
+	}
+	if isCheck == false {
+		return nil, errors.New(lang.L("errorFFplay"))
+	}
+
 	return &ffplay{
 		path: path,
-	}
+	}, nil
 }
 
-func (f *ffplay) SetPath(path string) {
-	f.path = path
+func (f *ffplay) GetPath() string {
+	return f.path
+}
+
+func checkFFplayPath(path string) (bool, error) {
+	cmd := exec.Command(path, "-version")
+	utils.PrepareBackgroundCommand(cmd)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return false, err
+	}
+	if strings.Contains(strings.TrimSpace(string(out)), "ffplay") == false {
+		return false, nil
+	}
+	return true, nil
 }