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/index.ts

@@ -0,0 +1,31 @@
+/**
+ * SEO Schema Module
+ * JSON-LD structured data generation for SEO
+ */
+
+// Types
+export type {
+  ProductSchema,
+  ReviewSchema,
+  OrganizationSchema,
+  WebSiteSchema,
+  BreadcrumbListSchema,
+  SchemaType,
+} from './types';
+
+// Schema generators (pure functions)
+export {
+  generateProductSchema,
+  generateCategorizedProductSchema,
+} from './productSchema';
+
+export {
+  generateOrganizationSchema,
+  generateWebSiteSchema,
+} from './organizationSchema';
+
+export {
+  generateBreadcrumbSchema,
+  generateProductBreadcrumbs,
+  generatePageBreadcrumbs,
+} from './breadcrumbSchema';