feat: add core i18n runtime and catalogs

lib/i18n/date-fns.ts

@@ -0,0 +1,13 @@
+import { enUS, fr, tr } from "date-fns/locale";
+
+export function getDateFnsLocale(locale: string) {
+  const normalized = locale.split("-")[0];
+  if (normalized === "tr") return tr;
+  if (normalized === "fr") return fr;
+  return enUS;
+}
+
+export function getDocumentDateFnsLocale() {
+  if (typeof document === "undefined") return tr;
+  return getDateFnsLocale(document.documentElement.lang || "tr");
+}