It appears that the repository has undergone several changes and renamings:

backend/node_modules/date-fns/isYesterday.d.cts

@@ -1,28 +0,0 @@
-import type { ContextOptions, DateArg } from "./types.js";
-/**
- * The {@link isYesterday} function options.
- */
-export interface IsYesterdayOptions extends ContextOptions<Date> {}
-/**
- * @name isYesterday
- * @category Day Helpers
- * @summary Is the given date yesterday?
- * @pure false
- *
- * @description
- * Is the given date yesterday?
- *
- * @param date - The date to check
- * @param options - An object with options
- *
- * @returns The date is yesterday
- *
- * @example
- * // If today is 6 October 2014, is 5 October 14:00:00 yesterday?
- * const result = isYesterday(new Date(2014, 9, 5, 14, 0))
- * //=> true
- */
-export declare function isYesterday(
-  date: DateArg<Date> & {},
-  options?: IsYesterdayOptions | undefined,
-): boolean;