feat: client-side currency conversion with admin-configurable rates

- CurrencyRatesService: RUB-based rates, persisted via localStorage
- CurrencyConvertPipe: impure pipe converting item price to selected currency
- Admin settings page: editable currency rates form
- Applied conversion to product-card, product-information, quick-view-dialog,
  delivery-information, compare-table, cart totals + payment payload

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

src/app/components/product-card/product-card.component.ts

@@ -1,9 +1,11 @@
-import { ChangeDetectionStrategy, Component, EventEmitter, Input, Output } from '@angular/core';
+import { ChangeDetectionStrategy, Component, EventEmitter, Input, Output, inject } from '@angular/core';
 import { DecimalPipe } from '@angular/common';
 import { RouterLink } from '@angular/router';
 import { Product } from '../../core/products/models/product-domain.model';
 import { LangRoutePipe } from '../../pipes/lang-route.pipe';
 import { TranslatePipe } from '../../i18n/translate.pipe';
+import { CurrencyConvertPipe } from '../../pipes/currency-convert.pipe';
+import { LanguageService } from '../../services/language.service';
 import { cleanDescription, getBadgeClass, getDiscountedPrice, getMainImage, onImageError } from '../../utils/item.utils';
 
 const STOCK_LABEL_KEYS: Record<string, string> = {
@@ -18,12 +20,15 @@ export type ProductCardAppearance = 'standard' | 'compact';
 @Component({
   selector: 'app-product-card',
   standalone: true,
-  imports: [DecimalPipe, RouterLink, LangRoutePipe, TranslatePipe],
+  imports: [DecimalPipe, RouterLink, LangRoutePipe, TranslatePipe, CurrencyConvertPipe],
   templateUrl: './product-card.component.html',
   styleUrls: ['./product-card.component.scss'],
   changeDetection: ChangeDetectionStrategy.OnPush
 })
 export class ProductCardComponent {
+  private readonly languageService = inject(LanguageService);
+  readonly displayCurrency = this.languageService.currentCurrency;
+
   @Input({ required: true }) item!: Product;
   @Input() title = '';
   @Input() description = '';