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

backend/node_modules/date-fns/locale/es.js

@@ -1,32 +0,0 @@
-import { formatDistance } from "./es/_lib/formatDistance.js";
-import { formatLong } from "./es/_lib/formatLong.js";
-import { formatRelative } from "./es/_lib/formatRelative.js";
-import { localize } from "./es/_lib/localize.js";
-import { match } from "./es/_lib/match.js";
-
-/**
- * @category Locales
- * @summary Spanish locale.
- * @language Spanish
- * @iso-639-2 spa
- * @author Juan Angosto [@juanangosto](https://github.com/juanangosto)
- * @author Guillermo Grau [@guigrpa](https://github.com/guigrpa)
- * @author Fernando Agüero [@fjaguero](https://github.com/fjaguero)
- * @author Gastón Haro [@harogaston](https://github.com/harogaston)
- * @author Yago Carballo [@YagoCarballo](https://github.com/YagoCarballo)
- */
-export const es = {
-  code: "es",
-  formatDistance: formatDistance,
-  formatLong: formatLong,
-  formatRelative: formatRelative,
-  localize: localize,
-  match: match,
-  options: {
-    weekStartsOn: 1 /* Monday */,
-    firstWeekContainsDate: 1,
-  },
-};
-
-// Fallback for modularized imports:
-export default es;