Add bilingual (EN/VI) documentation comments to @code blocks explaining the intended real data sources for each group: - Payment (11 files): order context workflow state - Operations (5 files): shift/cash management API - Dialogs (8 files): current order/product context Also add @using WebClientTpos.Client.Services to all 24 files for future service integration pattern, plus @inject PosDataService DataService to PendingOrders.razor specifically. No UI template, CSS, or demo data changes — comments only. Co-authored-by: Velik <hongochai10@users.noreply.github.com>