Add article.listSearchIndex for client-side search preload

Returns all company articles with id, sku, name, and eans as a flat
array. Walks the category tree to find reachable articles. Single
query using recursive CTE + FOR JSON for eans.

src/store/article/listSearchIndex.js

@@ -0,0 +1,23 @@
+import { SEARCH_ARTICLES } from '../../sql/article.js';
+import resolveCompanyAccess from '../companyuser/resolveCompanyAccess.js';
+
+export default function listSearchIndex(pool) {
+  const access = resolveCompanyAccess(pool);
+
+  return async (googleAuthId, companyId) => {
+    const { rootCategoryId, languageId } = await access(googleAuthId, companyId);
+
+    const result = await pool
+      .request()
+      .input('rootCategoryId', rootCategoryId)
+      .input('languageId', languageId)
+      .query(SEARCH_ARTICLES);
+
+    return result.recordset.map((row) => ({
+      id: row.id,
+      sku: row.sku,
+      name: row.name,
+      eans: row.eansJson ? JSON.parse(row.eansJson).map((r) => r.ean) : [],
+    }));
+  };
+}