fix(backoffice): WCAG 2.1 AA accessibility fixes

RC A11Y-01 audit pass, Backoffice (admin/*) area. Builds on 712a7b4/63c9cee's
composition pass (scope="col", skeletons, empty-states) without redoing that
work.

- Sidebar nav landmark: admin-layout's <nav aria-label> reused the
  "Dashboard" nav-item translation key as its landmark label, misleadingly
  announcing the whole sidebar as "Dashboard" - added a dedicated
  adminShell.sidebarLabel key ("Admin sidebar navigation") in en/ru/hy.
  Skip link, #admin-content main landmark, Escape handling, and mobile-drawer
  focus management were already correct - verified, not touched.

- Categories tree drag-and-drop keyboard fallback (WCAG 2.1.1): the category
  tree's native HTML5 DnD (draggable/dragstart/drop) reorders siblings with
  no keyboard equivalent - existing arrow-key tree navigation only expands/
  collapses/selects, never reorders. Added per-row move-up/move-down icon
  buttons (disabled at sibling boundaries), reusing the existing `reorder`
  output so the facade's reorder logic is untouched; new
  adminCategories.moveUp/moveDown keys in en/ru/hy.

- Screen-reader loading announcements: skeleton-row loading states across
  Products, Categories, Customers, Orders, Transactions, Users, Reviews,
  Monitoring (webhooks/events), and Analytics (summary cards + top products)
  were purely visual (app-skeleton is aria-hidden by design) with no
  accessible "loading" text, unlike the storefront/product-details pattern -
  added role="status"/aria-live="polite"/aria-busy + sr-only text using the
  existing common.loading key.

- Table row headers: added scope="row" to the primary identifying cell
  (product/category/customer name, order number, transaction order number,
  user name, review customer, report target, top-products/low-stock product
  name, webhook endpoint) on 9 tables that only had scope="col". Added
  matching `tbody th[scope='row'] { font-weight/color/text-align/
  vertical-align }` + last-row border resets in each component's own scss so
  the semantic change doesn't alter visuals (the shared app-table stylesheet
  styles all <th> as bold/muted by default).

Verified via `git show --stat` of fb1afb7/a03260e and `docs/UI-COMPOSITION-
REVIEW.md`'s Backoffice sections first, per instructions - confirmed
scope="col" coverage already complete, all admin modals already route
through the shared app-dialog (focus-trap/Escape/return-focus already
correct, nothing to fix), and the bare-<select> filters still carry
aria-label per the accepted Sprint 28 decision (not re-migrated to
app-select).

Flagged, not fixed:
- No toast/notification system exists anywhere in this codebase (product/
  category save and delete call the gateway with no success/error UI at
  all, not even a subscribe error handler) - there is nothing to wire
  aria-live onto without adding a new UI mechanism, which is out of scope
  for an a11y-only pass. A prerequisite feature-level fix, not an a11y
  regression.
- Dashboard's per-card metric/status-row/timeline skeletons (dashboard-
  metric, dashboard-status-row, dashboard-timeline) were left without
  aria-live wiring - wrapping each of the ~10 simultaneous mini-widgets in
  its own live region would fire a burst of redundant announcements; needs
  a single page-level "loading dashboard" region instead, a larger change
  than this surgical pass.
- Monitoring's events table and the notifications dropdown (role="menu"
  with a static empty-state message, aria-haspopup="true") were left as-is -
  matches the same partial-widget-pattern precedent already accepted for
  locale-tabs/product-tabs in the storefront and builder passes.
- Analytics `lowStockProducts` table's missing loading-skeleton branch
  (already flagged, not fixed, in the RC-Visual-02 pass) - untouched again
  here for the same reason.

Verified: npx tsc --noEmit clean; npm run build green (only the pre-existing
768.57 kB vs 700 kB initial-bundle budget warning, unrelated to this pass).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/features/admin/analytics/pages/admin-analytics-page.component.html

@@ -29,10 +29,11 @@
   @if (activeTab() === 'overview') {
     <div class="panel" role="tabpanel" id="panel-overview" aria-labelledby="tab-overview">
       @if (facade.loading()) {
-        <div class="summary-grid">
+        <div class="summary-grid" role="status" aria-live="polite" aria-busy="true">
           @for (i of [1,2,3,4,5,6]; track i) {
             <app-skeleton shape="rect" height="64px" />
           }
+          <span class="sr-only">{{ 'common.loading' | translate }}</span>
         </div>
       } @else if (facade.summary(); as summary) {
         <div class="summary-grid">
@@ -58,8 +59,9 @@
         <div class="card">
           <h2>{{ 'adminAnalytics.topProducts' | translate }}</h2>
           @if (facade.loading()) {
-            <div class="skeleton-rows">
+            <div class="skeleton-rows" role="status" aria-live="polite" aria-busy="true">
               @for (i of [1,2,3]; track i) { <app-skeleton shape="rect" height="36px" /> }
+              <span class="sr-only">{{ 'common.loading' | translate }}</span>
             </div>
           } @else if (facade.topProducts().length === 0) {
             <app-empty-state [title]="'adminAnalytics.topProductsEmptyTitle' | translate" [description]="'adminAnalytics.topProductsEmptyDescription' | translate" />
@@ -68,7 +70,7 @@
               <thead><tr><th scope="col">{{ 'adminProducts.name' | translate }}</th><th scope="col">{{ 'adminAnalytics.quantitySold' | translate }}</th><th scope="col">{{ 'adminAnalytics.revenue' | translate }}</th></tr></thead>
               <tbody>
                 @for (product of facade.topProducts(); track product.productId) {
-                  <tr><td>{{ product.name }}</td><td>{{ product.quantity }}</td><td>{{ product.revenue }}</td></tr>
+                  <tr><th scope="row">{{ product.name }}</th><td>{{ product.quantity }}</td><td>{{ product.revenue }}</td></tr>
                 }
               </tbody>
             </app-table>
@@ -85,7 +87,7 @@
               <tbody>
                 @for (product of facade.lowStockProducts(); track product.productId) {
                   <tr>
-                    <td>{{ product.name }}</td>
+                    <th scope="row">{{ product.name }}</th>
                     <td>{{ product.quantity }}</td>
                     <td><app-badge [variant]="product.stockStatus === 'out_of_stock' ? 'danger' : 'warning'">{{ ('adminProducts.' + (product.stockStatus === 'out_of_stock' ? 'outOfStock' : 'lowStock')) | translate }}</app-badge></td>
                   </tr>

src/app/features/admin/analytics/pages/admin-analytics-page.component.scss

@@ -55,3 +55,8 @@
   .summary-grid { grid-template-columns: 1fr; }
   .tabs { overflow-x: auto; flex-wrap: nowrap; }
 }
+
+// scope="row" on the product-name cell (a11y row header) must render
+// identically to a plain <td> - only the semantics change, not the visuals.
+tbody th[scope='row'] { font-weight: inherit; color: inherit; text-align: left; vertical-align: middle; }
+tbody tr:last-child th[scope='row'] { border-bottom: none; }