docs: add JSDoc headers to all externally exported store functions

src/store/category/addImage.js

@@ -5,6 +5,17 @@ import newFullHash from '../../util/newFullHash.js';
 import request from '../request.js';
 import resolveCategoryAccess from './resolveCategoryAccess.js';
 
+/**
+ * Adds an image to a category, processing it into AVIF full and thumb variants.
+ *
+ * @param {object} pool - The mssql connection pool.
+ * @returns {Function} An async function that adds a category image.
+ *
+ * @example
+ * const fn = addImage(pool);
+ * const result = await fn(42, 5, imageBuffer);
+ * // => { id, fullHash, thumbW, thumbH, thumbHash }
+ */
 export default function addImage(pool) {
   const access = resolveCategoryAccess(pool);