Fix /share and cleanup and reorganize frontend locale loading (#25240)

app/javascript/mastodon/locales/index.ts

@@ -0,0 +1,5 @@
+export type { LocaleData } from './global_locale';
+export { setLocale, getLocale, isLocaleLoaded } from './global_locale';
+export { loadLocale } from './load_locale';
+
+export { IntlProvider } from './intl_provider';