Complete UI rebuild of /platform/services/billing/ to match the Email Settings module design pattern. Now uses: teal bg-custom header bar with site name, 4 widget-box-two stat cards (Plan, Estimated Monthly, Next Billing, Status), horizontal Bootstrap nav-tabs with icons (Overview, Invoices, Subscription, Usage, Payment Methods, Payment History, Reports), card-box panels with header-title headings and descriptions, input-group-addon with icons for forms, label badges for statuses, single-page tabbed layout with lazy-loading (tabs load data on first click). Converted from 8 separate page files to single overview.php with all tabs. pagedata.php simplified to single entry point.