docs: add JSDoc headers to all externally exported store functions

src/store/delivery/getById.js

@@ -1,6 +1,17 @@
 import resolveCompanyAccess from '../companyuser/resolveCompanyAccess.js';
 import { loadDelivery } from './helpers.js';
 
+/**
+ * Returns a single delivery by its id within a company.
+ *
+ * @param {object} pool - The mssql connection pool.
+ * @returns {Function} An async function that fetches a delivery by id.
+ *
+ * @example
+ * const fn = getById(pool);
+ * const delivery = await fn(42, 1, 5);
+ * // => { id, number, type, entityId, date, lines: [...] }
+ */
 export default function getById(pool) {
   const access = resolveCompanyAccess(pool);