Add theme management functionality to the application

Implemented a theme management system allowing users to select and persist themes (default, light, dark) in the settings menu.

handler/menu.go

@@ -5,6 +5,7 @@ import (
 	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/kernel"
 	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/localizer"
 	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/menu"
+	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/theme"
 	"github.com/nicksnyder/go-i18n/v2/i18n"
 )
 
@@ -20,6 +21,7 @@ type MenuHandler struct {
 	menuViewSetting     menu.ViewSettingContract
 	localizerView       localizer.ViewContract
 	localizerRepository localizer.RepositoryContract
+	themeService        theme.ThemeContract
 }
 
 func NewMenuHandler(
@@ -29,6 +31,7 @@ func NewMenuHandler(
 	menuViewSetting menu.ViewSettingContract,
 	localizerView localizer.ViewContract,
 	localizerRepository localizer.RepositoryContract,
+	themeService theme.ThemeContract,
 ) *MenuHandler {
 	return &MenuHandler{
 		app:                 app,
@@ -37,6 +40,7 @@ func NewMenuHandler(
 		menuViewSetting:     menuViewSetting,
 		localizerView:       localizerView,
 		localizerRepository: localizerRepository,
+		themeService:        themeService,
 	}
 }
 
@@ -154,6 +158,12 @@ func (h MenuHandler) settingsSelection() {
 		if err != nil {
 			return err
 		}
+
+		err = h.themeService.SetCurrentTheme(setting.ThemeInfo)
+		if err != nil {
+			return err
+		}
+
 		h.convertorHandler.MainConvertor()
 		return nil
 	}