fix(storefront): WCAG 2.1 AA accessibility fixes

RC A11Y-01 audit pass, storefront + shared app-shell chrome only. Builds
on RC-Visual-02/RC-Premium-01/RC STORE-01 without redoing that work.

- Skip link: added first-focusable "skip to main content" link (app.html,
  styles.scss .skip-link/.sr-only), targeting new #main-content landmark.
  New app.skipToContent i18n key in en/ru/hy.
- Header: mobile menu items stayed keyboard-focusable and screen-reader
  reachable while visually collapsed (max-height:0 with no visibility
  toggle) - fixed with visibility:hidden + matched transition-delay.
  Desktop search input (readonly, click-to-navigate) had no keyboard
  activation - added aria-label + (keydown.enter).
- Cart payment/bank-payment modals: custom (non-app-dialog) UI had no
  focus trap, no Escape handling, and never returned focus to the
  triggering element - ported app-dialog's confirmed-correct
  focus-trap/Escape/return-focus pattern directly onto cart.component.ts.
  Added role="dialog"/aria-modal/aria-label to both panels and
  role="status"|"alert"/aria-live to every payment-status screen so
  screen readers announce state changes (creating/waiting/success/
  error/timeout).
- Search combobox: suggestion listbox had no role="combobox" wiring on
  the input and suggestion buttons weren't role="option" - added
  aria-autocomplete, aria-controls, aria-activedescendant, aria-selected
  so the existing arrow-key navigation is announced to screen readers.
- Product tabs: tablist/tab pattern was incomplete (no role="tablist",
  no tabpanel) - added role="tablist" + ids to product-tabs.component,
  role="tabpanel"/aria-labelledby to the content panel in
  product-details-container.
- Review form: rating/text validation errors weren't associated with
  their controls (no aria-describedby, no role="alert") - fixed; added
  aria-required to the review textarea.
- delivery-selector: added aria-required to the delivery <select> when
  a selection is mandatory.
- Shared app-icon component: doc comment claimed "decorative by default
  (aria-hidden)" but no aria-hidden was ever applied - fixed to actually
  set aria-hidden="true" when undecorated, and role="img"/aria-label
  when ariaLabel is passed. Shared component, affects every icon-only
  usage app-wide, no visual change.
- Color contrast: --text-light fails WCAG AA 4.5:1 for normal text in
  every theme (dexar 3.39:1, lavero/novo 2.54:1 against white). The two
  in-scope usages (company-details org-short/basis, review-form
  upload-placeholder) switched to --text-secondary (4.55:1-7.56:1,
  passes), same visual family, no layout change.

Flagged, not fixed (design-system decisions, not polish):
- --border-color fails WCAG 1.4.11 3:1 for UI-component boundaries in
  every theme (dexar 1.42:1, lavero/novo 1.24:1 vs white) - pervasive
  token used by hundreds of borders app-wide; needs theme-owner sign-off.
- --success-color/--warning-color/--error-color/--info-color used as
  plain text-on-white in several places (product-information,
  question-card, review-form, compare-page) fail 4.5:1 (2.15-3.76:1) -
  genuine brand semantic colors, changing them to pass would visibly
  shift the palette; needs a deliberate token decision.
- Header mobile-menu max-height/padding transition (pre-existing,
  unrelated to this fix) flagged by design lint as layout-thrashing;
  left as-is per the "no layout/business-logic changes" constraint.

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

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

src/app/pages/cart/cart.component.html

@@ -195,12 +195,12 @@
 <!-- Payment Popup Modal -->
 @if (showPaymentPopup()) {
   <div class="payment-modal-overlay">
-    <div class="payment-modal">
+    <div class="payment-modal" #paymentModalPanel role="dialog" aria-modal="true" [attr.aria-label]="'cart.checkout' | translate" tabindex="-1">
       <button class="close-modal-btn" (click)="closePaymentPopup()" [attr.aria-label]="'cart.close' | translate">
         <app-icon name="x" [size]="20" />
       </button>
       @if (paymentStatus() === 'creating') {
-        <div class="payment-status-screen">
+        <div class="payment-status-screen" role="status" aria-live="polite">
           <div class="spinner-large"></div>
           <h2>{{ 'cart.creatingPayment' | translate }}</h2>
           <p>{{ 'cart.waitFewSeconds' | translate }}</p>
@@ -208,7 +208,7 @@
       }
 
       @if (paymentStatus() === 'waiting') {
-        <div class="payment-active">
+        <div class="payment-active" role="status" aria-live="polite">
           <h2>{{ selectedPaymentMethod() === 'card' ? ('cart.waitingPayment' | translate) : ('cart.scanQr' | translate) }}</h2>
           
           @if (qrCodeUrl()) {
@@ -246,7 +246,7 @@
       }
 
       @if (paymentStatus() === 'error') {
-        <div class="payment-status-screen error">
+        <div class="payment-status-screen error" role="alert" aria-live="assertive">
           <div class="error-icon" aria-hidden="true">!</div>
           <h2>{{ 'cart.paymentError' | translate }}</h2>
           <p>{{ 'cart.paymentErrorDesc' | translate }}</p>
@@ -260,14 +260,14 @@
       }
 
       @if (paymentStatus() === 'success') {
-        <div class="payment-status-screen success">
+        <div class="payment-status-screen success" role="status" aria-live="polite">
           <div class="success-icon" aria-hidden="true">✓</div>
           <h2>{{ 'cart.paymentSuccess' | translate }}</h2>
         </div>
       }
 
       @if (paymentStatus() === 'timeout') {
-        <div class="payment-status-screen timeout">
+        <div class="payment-status-screen timeout" role="status" aria-live="polite">
           <div class="timeout-icon" aria-hidden="true">⏱</div>
           <h2>{{ 'cart.paymentTimeout' | translate }}</h2>
           <p>{{ 'cart.paymentTimeoutDesc' | translate }}</p>
@@ -278,7 +278,7 @@
 
     @if (showBankPaymentPopup() && bankPaymentFrameUrl()) {
       <div class="bank-payment-modal-overlay">
-        <div class="bank-payment-modal">
+        <div class="bank-payment-modal" #bankPaymentModalPanel role="dialog" aria-modal="true" [attr.aria-label]="'cart.payViaCard' | translate" tabindex="-1">
           <button class="close-modal-btn" (click)="closeBankPaymentPopup()" [attr.aria-label]="'cart.close' | translate">
             <app-icon name="x" [size]="20" />
           </button>