deps: i18next 10 -> 23, react-i18next 7 -> 14

Modernizes the whole i18n stack:
- 48 translate([], {wait:true}) / translate() HOCs -> withTranslation()
- react.wait:true -> react.useSuspense:false
- whitelist -> supportedLngs; added compatibilityJSON: 'v3' so our
  natural-language keys + v3 _plural layout keep working (custom
  separators ss/eth/dj preserved)
- backends: xhr -> i18next-http-backend (client), sync-fs ->
  i18next-fs-backend (server); dropped i18next-localstorage-cache
  (was enabled:false); languagedetector 2 -> 8
- ReSendEmail: <Interpolate> (removed in v10) -> <Trans values={{email}}/>,
  dropped the removed bare t export
- saveMissing handler signature (lngs, ns, key, fallbackValue)

Silences the per-component Translate/I18n legacy-context warnings.
Browser-verified es/en switch and <Trans> interpolation on /fires;
REST smoke byte-identical.

imports/startup/server/i18n.js

@@ -1,6 +1,6 @@
 import { Meteor } from 'meteor/meteor';
 import i18n from 'i18next';
-import backend from 'i18next-sync-fs-backend';
+import backend from 'i18next-fs-backend';
 import i18nOpts from '../common/i18n';
 // import moment from 'moment';
 // import { T9n } from 'meteor-accounts-t9n';