feat: implement programmatic SEO for solutions pages

- Add 10 oil-for-concern solution pages with localized slugs
- Support 4 languages: sr, en, de, fr with proper canonical URLs
- Add solutions hub, by-concern, and by-oil directory pages
- Filter bundle products from solutions pages
- Add hideLangSwitcher prop to Header component
- Update translations for all languages
- Fix canonical URLs to include locale prefix

src/lib/programmatic-seo/dataLoader.ts

@@ -2,7 +2,8 @@ import { readFile } from "fs/promises";
 import { join } from "path";
 import type { 
   OilForConcernPage,
-  LocalizedSEOKeywords
+  LocalizedSEOKeywords,
+  LocalizedString
 } from "./types";
 
 const DATA_DIR = join(process.cwd(), "data");
@@ -63,17 +64,24 @@ export async function getAllOilForConcernPages(): Promise<OilForConcernPage[]> {
 }
 
 export async function getAllSolutionSlugs(): Promise<Array<{ locale: string; slug: string }>> {
-  const slugs = await getAllOilForConcernSlugs();
+  const pages = await getAllOilForConcernPages();
   const result: Array<{ locale: string; slug: string }> = [];
   
-  for (const slug of slugs) {
+  for (const page of pages) {
     for (const locale of ["sr", "en", "de", "fr"] as const) {
       result.push({
         locale,
-        slug
+        slug: page.localizedSlugs[locale]
       });
     }
   }
   
   return result;
 }
+
+export async function getOilForConcernPageBySlug(slug: string, locale: string): Promise<OilForConcernPage | null> {
+  const pages = await getAllOilForConcernPages();
+  return pages.find(page => 
+    page.localizedSlugs[locale as "sr" | "en" | "de" | "fr"] === slug
+  ) || null;
+}