fix(about): show real ClickOnce deployment version in Settings → About

The About tab was always showing "1.0.0" because it read the DLL's
AssemblyVersion, which we never bumped in source — even when the
ClickOnce manifest had been rolled to 1.1.0 by the CI tag.

Read System.Deployment.Application.ApplicationDeployment.CurrentDeployment
.CurrentVersion at runtime when the add-in is running under ClickOnce
(IsNetworkDeployed=true). That's the version the user actually
installed. Fall back to AssemblyVersion when dev-running under F5 (no
ClickOnce context). Adds System.Deployment GAC reference to the UI
project.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/OutlookAddin.UI/OutlookAddin.UI.csproj

@@ -18,6 +18,7 @@
 
   <ItemGroup>
     <Reference Include="System.Net.Http" />
+    <Reference Include="System.Deployment" />
   </ItemGroup>
 
   <ItemGroup>

src/OutlookAddin.UI/ViewModels/SettingsViewModel.cs

@@ -70,8 +70,32 @@ namespace MarcusLaw.OutlookAddin.UI.ViewModels
             Username = creds?.Username ?? string.Empty;
             InitialApiKey = creds?.ApiKey ?? string.Empty;
 
-            var version = typeof(SettingsViewModel).Assembly.GetName().Version?.ToString() ?? "1.0.0";
-            VersionLine = $"גרסה {version}";
+            VersionLine = $"גרסה {ResolveDisplayVersion()}";
+        }
+
+        /// <summary>
+        /// Picks the most accurate version to surface in the About tab:
+        /// the ClickOnce activation version when the add-in is installed
+        /// over the wire (auto-updated to the real deployment version),
+        /// else the assembly's AssemblyVersion (which is set per-source
+        /// and may lag behind the deployed ClickOnce manifest).
+        /// </summary>
+        private static string ResolveDisplayVersion()
+        {
+            try
+            {
+                if (System.Deployment.Application.ApplicationDeployment.IsNetworkDeployed)
+                {
+                    return System.Deployment.Application.ApplicationDeployment
+                        .CurrentDeployment.CurrentVersion.ToString();
+                }
+            }
+            catch
+            {
+                // Not running under ClickOnce (dev / F5), or System.Deployment
+                // is not available — fall through to the AssemblyVersion.
+            }
+            return typeof(SettingsViewModel).Assembly.GetName().Version?.ToString() ?? "1.0.0";
         }
 
         /// <summary>