customizable packet fragmentation settings (#9597)

* first changes

* fix: use ItemsSource for fragment packets ComboBox so value saves correctly

* feat: add customizable packet fragmentation for Xray-core

- Add fragment settings in Core tab: Packets (dropdown), Length (range), Interval (range), MaxSplit (0-10000)
- Support both 'from-to' (e.g., 50-100) and single value (e.g., 50) formats for Length, Interval, and MaxSplit
- Validation with shortened error message: 'Invalid range format. Use from-to (e.g., 50-100).'
- UI in PopupBox (materialDesign) visible only when EnableFragment is checked
- Only Xray-core supported (Mihomo/sing-box fragment code removed)
- Localization updated for 8 languages

* fix: address 2dust review feedback

- Move FragmentPacketsOptions to Global class
- Remove default values from Fragment4RayItem model (set in ConfigHandler)
- Fix Avalonia bindings: move ItemsSource and SelectedItem to code-behind
- Update ViewModel to use Global.FragmentPacketsOptions
- Remove defaults from model properties

* Adjust ui

---------

Co-authored-by: 2dust <31833384+2dust@users.noreply.github.com>

v2rayN/ServiceLib/Common/Utils.cs

@@ -576,6 +576,58 @@ public class Utils
         }
     }
 
+    public static bool TryParseRange(string? input, int min, int max, out int from, out int to)
+    {
+        from = to = 0;
+        if (string.IsNullOrWhiteSpace(input))
+        {
+            return true;
+        }
+        var parts = input.Split('-');
+        if (parts.Length == 1)
+        {
+            if (!int.TryParse(parts[0], out from))
+            {
+                return false;
+            }
+            to = from;
+            return from >= min && to <= max;
+        }
+        if (parts.Length != 2
+            || !int.TryParse(parts[0], out from)
+            || !int.TryParse(parts[1], out to))
+        {
+            return false;
+        }
+        return from >= min && to <= max && from <= to;
+    }
+
+    public static bool TryParseMaxSplit(string? input, int min, int max, out int from, out int to)
+    {
+        from = to = 0;
+        if (string.IsNullOrWhiteSpace(input))
+        {
+            return true;
+        }
+        var parts = input.Split('-');
+        if (parts.Length == 1)
+        {
+            if (!int.TryParse(parts[0], out from))
+            {
+                return false;
+            }
+            to = from;
+            return from >= min && to <= max;
+        }
+        if (parts.Length != 2
+            || !int.TryParse(parts[0], out from)
+            || !int.TryParse(parts[1], out to))
+        {
+            return false;
+        }
+        return from >= min && to <= max && from <= to;
+    }
+
     public static bool IsPrivateNetwork(string ip)
     {
         if (IPAddress.TryParse(ip, out var address))