feat: comprehensive SEO system with keywords and schema markup

- Add 4-locale keyword configurations (SR, EN, DE, FR)
- Create schema generators (Product, Organization, Breadcrumb)
- Add React components for JSON-LD rendering
- Implement caching for keyword performance
- Abstract all SEO logic for maintainability

src/lib/seo/schema/breadcrumbSchema.ts

@@ -0,0 +1,84 @@
+import { BreadcrumbListSchema } from './types';
+
+interface BreadcrumbItem {
+  name: string;
+  url?: string;  // Optional for last item (current page)
+}
+
+/**
+ * Generate BreadcrumbList schema (JSON-LD)
+ * Pure function - takes breadcrumb items, returns schema object
+ * 
+ * @param items - Array of breadcrumb items with name and optional URL
+ * @returns BreadcrumbListSchema object
+ * @example
+ * const breadcrumbs = [
+ *   { name: 'Home', url: 'https://example.com' },
+ *   { name: 'Products', url: 'https://example.com/products' },
+ *   { name: 'Product Name' }  // Current page (no URL)
+ * ];
+ * const schema = generateBreadcrumbSchema(breadcrumbs);
+ */
+export function generateBreadcrumbSchema(
+  items: BreadcrumbItem[]
+): BreadcrumbListSchema {
+  return {
+    '@context': 'https://schema.org',
+    '@type': 'BreadcrumbList',
+    itemListElement: items.map((item, index) => ({
+      '@type': 'ListItem',
+      position: index + 1,
+      name: item.name,
+      ...(item.url && { item: item.url }),  // Only include item if URL exists
+    })),
+  };
+}
+
+/**
+ * Generate standard breadcrumbs for product pages
+ * 
+ * @param baseUrl - Site base URL
+ * @param locale - Locale code
+ * @param productName - Product name
+ * @param productSlug - Product slug
+ * @returns BreadcrumbListSchema object
+ */
+export function generateProductBreadcrumbs(
+  baseUrl: string,
+  locale: string,
+  productName: string,
+  productSlug: string
+): BreadcrumbListSchema {
+  const localePrefix = locale === 'sr' ? '' : `/${locale}`;
+  
+  const items: BreadcrumbItem[] = [
+    { name: 'Home', url: `${baseUrl}${localePrefix || '/'}` },
+    { name: 'Products', url: `${baseUrl}${localePrefix}/products` },
+    { name: productName },  // Current page
+  ];
+
+  return generateBreadcrumbSchema(items);
+}
+
+/**
+ * Generate breadcrumbs for static pages
+ * 
+ * @param baseUrl - Site base URL
+ * @param locale - Locale code
+ * @param pageName - Current page name
+ * @returns BreadcrumbListSchema object
+ */
+export function generatePageBreadcrumbs(
+  baseUrl: string,
+  locale: string,
+  pageName: string
+): BreadcrumbListSchema {
+  const localePrefix = locale === 'sr' ? '' : `/${locale}`;
+  
+  const items: BreadcrumbItem[] = [
+    { name: 'Home', url: `${baseUrl}${localePrefix || '/'}` },
+    { name: pageName },  // Current page
+  ];
+
+  return generateBreadcrumbSchema(items);
+}