feat(18-01): models, SettingsService, OwnershipElevationService + tests

- AppSettings.AutoTakeOwnership bool property defaulting to false
- PermissionEntry.WasAutoElevated optional param (default false, last position)
- SettingsService.SetAutoTakeOwnershipAsync persists toggle
- IOwnershipElevationService interface + OwnershipElevationService wrapping Tenant.SetSiteAdmin
- SettingsViewModel.AutoTakeOwnership property loads and persists via SetAutoTakeOwnershipAsync
- DI registration in App.xaml.cs (Phase 18 section)
- 8 new tests: models, persistence, service, viewmodel

SharepointToolbox/App.xaml.cs

@@ -161,6 +161,9 @@ public partial class App : Application
         // Phase 17: Group Expansion
         services.AddTransient<ISharePointGroupResolver, SharePointGroupResolver>();
 
+        // Phase 18: Auto-Take Ownership
+        services.AddTransient<IOwnershipElevationService, OwnershipElevationService>();
+
         // Phase 7: User Access Audit
         services.AddTransient<IUserAccessAuditService, UserAccessAuditService>();
         services.AddTransient<IGraphUserSearchService, GraphUserSearchService>();

SharepointToolbox/Core/Models/AppSettings.cs

@@ -4,4 +4,5 @@ public class AppSettings
 {
     public string DataFolder { get; set; } = string.Empty;
     public string Lang { get; set; } = "en";
+    public bool AutoTakeOwnership { get; set; } = false;
 }

SharepointToolbox/Core/Models/PermissionEntry.cs

@@ -13,5 +13,6 @@ public record PermissionEntry(
     string UserLogins,          // Semicolon-joined login names
     string PermissionLevels,    // Semicolon-joined role names (Limited Access already removed)
     string GrantedThrough,      // "Direct Permissions" | "SharePoint Group: <name>"
-    string PrincipalType        // "SharePointGroup" | "User" | "External User"
+    string PrincipalType,       // "SharePointGroup" | "User" | "External User"
+    bool   WasAutoElevated = false  // Set to true when site admin was auto-granted to access this entry
 );

SharepointToolbox/Services/IOwnershipElevationService.cs

@@ -0,0 +1,8 @@
+using Microsoft.SharePoint.Client;
+
+namespace SharepointToolbox.Services;
+
+public interface IOwnershipElevationService
+{
+    Task ElevateAsync(ClientContext tenantAdminCtx, string siteUrl, string loginName, CancellationToken ct);
+}

SharepointToolbox/Services/OwnershipElevationService.cs

@@ -0,0 +1,14 @@
+using Microsoft.Online.SharePoint.TenantAdministration;
+using Microsoft.SharePoint.Client;
+
+namespace SharepointToolbox.Services;
+
+public class OwnershipElevationService : IOwnershipElevationService
+{
+    public async Task ElevateAsync(ClientContext tenantAdminCtx, string siteUrl, string loginName, CancellationToken ct)
+    {
+        var tenant = new Tenant(tenantAdminCtx);
+        tenant.SetSiteAdmin(siteUrl, loginName, isSiteAdmin: true);
+        await tenantAdminCtx.ExecuteQueryAsync();
+    }
+}

SharepointToolbox/Services/SettingsService.cs

@@ -36,4 +36,11 @@ public class SettingsService
         settings.DataFolder = path;
         await _repository.SaveAsync(settings);
     }
+
+    public async Task SetAutoTakeOwnershipAsync(bool enabled)
+    {
+        var settings = await _repository.LoadAsync();
+        settings.AutoTakeOwnership = enabled;
+        await _repository.SaveAsync(settings);
+    }
 }

SharepointToolbox/ViewModels/Tabs/SettingsViewModel.cs

@@ -39,6 +39,19 @@ public partial class SettingsViewModel : FeatureViewModelBase
         }
     }
 
+    private bool _autoTakeOwnership;
+    public bool AutoTakeOwnership
+    {
+        get => _autoTakeOwnership;
+        set
+        {
+            if (_autoTakeOwnership == value) return;
+            _autoTakeOwnership = value;
+            OnPropertyChanged();
+            _ = _settingsService.SetAutoTakeOwnershipAsync(value);
+        }
+    }
+
     private string? _mspLogoPreview;
     public string? MspLogoPreview
     {
@@ -65,8 +78,10 @@ public partial class SettingsViewModel : FeatureViewModelBase
         var settings = await _settingsService.GetSettingsAsync();
         _selectedLanguage = settings.Lang;
         _dataFolder = settings.DataFolder;
+        _autoTakeOwnership = settings.AutoTakeOwnership;
         OnPropertyChanged(nameof(SelectedLanguage));
         OnPropertyChanged(nameof(DataFolder));
+        OnPropertyChanged(nameof(AutoTakeOwnership));
 
         var mspLogo = await _brandingService.GetMspLogoAsync();
         MspLogoPreview = mspLogo is not null ? $"data:{mspLogo.MimeType};base64,{mspLogo.Base64}" : null;