- StorageViewModel: add OnGlobalSitesChanged, OnSiteUrlChanged, _hasLocalSiteOverride
- SearchViewModel: add OnGlobalSitesChanged, OnSiteUrlChanged, _hasLocalSiteOverride
- DuplicatesViewModel: add OnGlobalSitesChanged, OnSiteUrlChanged, _hasLocalSiteOverride
- FolderStructureViewModel: add OnGlobalSitesChanged, OnSiteUrlChanged, _hasLocalSiteOverride
- All four VMs pre-fill SiteUrl from first global site; local typing sets override flag
- Tenant switch resets _hasLocalSiteOverride in all four VMs
- DuplicatesViewModel: ModeFiles/Folders, criteria checkboxes, group flattening to DuplicateRow
- Uses TenantProfile site URL override pattern (ctx.Url is read-only)
- ExportHtmlCommand exports DuplicateGroup list via DuplicatesHtmlExportService
- DuplicatesView.xaml: type selector, criteria panel + flattened DataGrid
- DuplicatesView.xaml.cs: DI constructor with DataContext wiring