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

static/js/app/ui.js

@@ -450,7 +450,9 @@ const ui = {
         this._hydrateViewIfNeeded('grid');
 
         filesGrid.style.display = 'grid';
+        filesGrid.classList.remove('hidden');
         filesListView.style.display = 'none';
+        filesListView.classList.add('hidden');
         gridViewBtn.classList.add('active');
         listViewBtn.classList.remove('active');
         window.app.currentView = 'grid';
@@ -469,7 +471,9 @@ const ui = {
         this._hydrateViewIfNeeded('list');
 
         filesGrid.style.display = 'none';
+        filesGrid.classList.add('hidden');
         filesListView.style.display = 'flex';
+        filesListView.classList.remove('hidden');
         gridViewBtn.classList.remove('active');
         listViewBtn.classList.add('active');
         window.app.currentView = 'list';