feat(frontend): i18n expansion, admin/profile i18n, grid/list view fix, empty state

- Add 5 new locales (hi, ar, ru, ja, ko) — now 14 total
- Admin panel: 117 i18n keys, confirm modal, animated tabs, no inline handlers
- Profile page: 58 i18n keys with data-i18n attributes
- Fix i18n safeT() shadowing bug and translationsLoaded timing
- Fix grid/list view: list header no longer shows in grid mode on login
- Fix classList.toggle hidden sync for view switching across all nav functions
- Revert .hidden important that broke login page rendering
- Add files empty state (no_files + empty_hint) with translations
- Fix language selector dropdown scroll and styling
- Fix admin panel scroll with sticky tabs

src/interfaces/nextcloud/preview_handler.rs

@@ -15,7 +15,7 @@ use crate::application::ports::file_ports::FileRetrievalUseCase;
 use crate::application::ports::storage_ports::FileReadPort;
 use crate::application::ports::thumbnail_ports::{ThumbnailPort, ThumbnailSize};
 use crate::common::di::AppState;
-use crate::interfaces::middleware::auth::CurrentUser;
+use crate::interfaces::middleware::auth::AuthUser;
 
 #[derive(Debug, Deserialize)]
 pub struct PreviewParams {
@@ -34,7 +34,7 @@ pub struct PreviewParams {
 /// - Size selection based on request dimensions and forceIcon param
 pub async fn handle_preview(
     State(state): State<Arc<AppState>>,
-    user: CurrentUser,
+    user: AuthUser,
     Query(params): Query<PreviewParams>,
 ) -> impl IntoResponse {
     // Parse the Nextcloud file ID — the NC app may append an instance suffix