docs: expand input and output object types in API signatures

src/store/manifestattachment/add.js

@@ -16,7 +16,7 @@ export default function add(pool) {
    * @param {string} input.mimetype - The MIME type of the file (e.g. `'application/pdf'`).
    * @param {string} input.name - The file name.
    * @param {Buffer} input.content - The file content.
-   * @returns {Promise<object>} The created attachment record.
+   * @returns {Promise<{id: number, manifestId: number, fileId: number, mimetype: string, name: string}>} The created attachment record.
    * @throws {Error} If the manifest is not found or file input is invalid.
    *
    * @example