Add Office 2016 support, bump to v1.20

Office 2016 Standard, Professional Plus, and Home & Business editions
added with PerpetualVL2019 channel for volume licenses.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Models/OfficeEdition.cs

@@ -99,6 +99,35 @@ namespace InstaSoftOfficeTool.Models
                         }
                     };
 
+                case OfficeVersion.Office2016:
+                    return new[]
+                    {
+                        new OfficeEdition
+                        {
+                            DisplayName = "Standard",
+                            Description = "Alapvető irodai alkalmazások: Word, Excel, PowerPoint, Outlook, OneNote",
+                            ProductId = "Standard2016Volume",
+                            Channel = "PerpetualVL2019",
+                            IsVolume = true
+                        },
+                        new OfficeEdition
+                        {
+                            DisplayName = "Professional Plus",
+                            Description = "Teljes csomag: Word, Excel, PowerPoint, Outlook, Access, Publisher, OneNote, Skype for Business",
+                            ProductId = "ProPlus2016Volume",
+                            Channel = "PerpetualVL2019",
+                            IsVolume = true
+                        },
+                        new OfficeEdition
+                        {
+                            DisplayName = "Otthoni és kisvállalati verzió",
+                            Description = "Word, Excel, PowerPoint, Outlook, OneNote — vállalkozásokban is használható",
+                            ProductId = "HomeBusiness2016Retail",
+                            Channel = "Current",
+                            IsVolume = false
+                        }
+                    };
+
                 default:
                     return new OfficeEdition[0];
             }

Models/OfficeVersion.cs

@@ -4,6 +4,7 @@ namespace InstaSoftOfficeTool.Models
     {
         Office2024,
         Office2021,
-        Office2019
+        Office2019,
+        Office2016
     }
 }