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>

.gitignore

@@ -84,6 +84,9 @@ StyleCopReport.xml
 *.rsp
 # but not Directory.Build.rsp, as it configures directory-level build defaults
 !Directory.Build.rsp
+bin/
+obj/
+build/
 *.sbr
 *.tlb
 *.tli