Create a dedicated i18next instance per SSR request and remove server context-storage coupling from translation runtime, while keeping a separate client singleton path.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Complete the i18n migration by switching runtime setup and remaining components to i18next-vue, and add shared locale constants/helpers for SSR and client language handling.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>