Improve speed stats, UI usability, and settings persistence

Enhanced speed counter with smoothing and elapsed time display.
Added folder open buttons to UI and repositioned speed label.
Added UpdateSubdirectories to settings for persistence.

imagecatalog/Models/SettingsDto.cs

@@ -177,6 +177,10 @@ namespace ImageCatalog_2.Models
         [XmlElement("GeneraleRotazioneAutomatica")]
         public bool AutomaticRotation { get; set; }
 
+        [JsonPropertyName("UpdateSubdirectories")]
+        [XmlElement("DirSottoDirectory")]
+        public bool UpdateSubdirectories { get; set; }
+
         [JsonPropertyName("AddRaceTime")]
         [XmlElement("TempoGara")]
         public bool AddRaceTime { get; set; }