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/common/i18n.js

@@ -40,13 +40,17 @@ const i18nOpts = {
       return value;
     }
   },
-  whitelist: ['es', 'en', 'gl'], // allowed languages
+  supportedLngs: ['es', 'en', 'gl'], // allowed languages (was `whitelist` pre-i18next-21)
   load: 'languageOnly', // 'es' o 'en', previously: 'all', // es-ES -> es, en-US -> en
   debug: shouldDebug,
   ns: 'common',
   defaultNS: 'common',
   saveMissing: shouldDebug, // if true seems it's fails to getResourceBundle
   saveMissingTo: 'es',
+  // Our locale JSON uses natural-language (Spanish) keys and the v3 plural
+  // layout (`key_plural`), so keep i18next on the v3 JSON format instead of
+  // the v4 suffix scheme (`key_one`/`key_other`).
+  compatibilityJSON: 'v3',
   keySeparator: 'ß',
   nsSeparator: 'ð',
   pluralSeparator: 'đ'