feat: enhance redis and production IA

backend/internal/handler/preferences.go

@@ -69,7 +69,7 @@ func UpdateUserPreferences(c *gin.Context) {
 // GET /api/v1/public/login-style (no auth required)
 func GetPublicLoginStyle(c *gin.Context) {
 	style := "split"
-	theme := "dark"
+	theme := "system"
 
 	var s model.SystemSetting
 	if model.DB.Where("`key` = ?", "login_style").Take(&s).Error == nil && s.Value != "" {