- errorDialog + hints now use createStore (drop their bespoke listener arrays).
- theme/sidebarLayout/notifications/App filters/Playlists plSort use readMerged/
readJSON/writeJSON instead of inline try/JSON.parse/catch.
- Stats, SettingsPanel and App's channel filter/view tabs use usePersistedState
(the 3 sites that reinvented usePersistedTab inline).
- Every siftlode.* key now sourced from the LS registry (no scattered literals).
Set up react-i18next with locale files auto-loaded per area (Vite glob), a compact
LanguageSwitcher, and language as a server-persisted preference (preferences.language)
mirrored to localStorage. On first login the default UI language is guessed from the
Google-reported locale (hu/en/de, else English). vite-env.d.ts types the build-time env.