feat: add red-green 3D mode and Windows Forms GUI

- add rg (red-green) anaglyph subtitle mode with configurable horizontal offset
- extend CLI mode handling to support sbs, ou, and rg
- add offsetx option for anaglyph subtitle positioning
- add Windows Forms GUI project for configuring and running conversions
- add file pickers for input/output paths in the GUI
- add GUI controls for mode, resolution, font size, and offset
- add status output and mode-aware UI behavior in the GUI
- update mode selection handling to support user-friendly display labels

ConvertSRTto3DASSGUI/Properties/Settings.Designer.cs

@@ -0,0 +1,30 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//     Runtime Version:4.0.30319.42000
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+namespace ConvertSRTto3DASSGUI.Properties
+{
+
+
+    [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "11.0.0.0")]
+    internal sealed partial class Settings : global::System.Configuration.ApplicationSettingsBase
+    {
+
+        private static Settings defaultInstance = ((Settings)(global::System.Configuration.ApplicationSettingsBase.Synchronized(new Settings())));
+
+        public static Settings Default
+        {
+            get
+            {
+                return defaultInstance;
+            }
+        }
+    }
+}