docs: add JSDoc headers to all externally exported store functions

src/store/article/getBySku.js

@@ -6,6 +6,18 @@ function parseJsonArray(raw) {
   return Array.isArray(arr) ? arr : [];
 }
 
+/**
+ * Returns the full detail of an article by its SKU, including unit, brand,
+ * categories, photos, EANs and prices.
+ *
+ * @param {object} pool - The mssql connection pool.
+ * @returns {Function} An async function that fetches an article by SKU.
+ *
+ * @example
+ * const fn = getBySku(pool);
+ * const article = await fn(42, 'SKU-1');
+ * // => { article: { id, sku, name, unit, brand, categoryIds, photos, eans, prices, ... } }
+ */
 export default function getBySku(pool) {
   return async (googleAuthId, sku) => {
     const t0 = performance.now();