Frontend optimizations: SVG icons, remove updateFileIcons, unify rendering, scope translatePage

- Replace Font Awesome CDN with inline SVG system (icons.js + MutationObserver)
- Remove updateFileIcons() (~140 lines) - redundant with backend icon_class + MutationObserver
- Migrate favorites.js and recent.js to use shared ui.renderFolders/renderFiles (eliminate ~260 lines of duplicate rendering + per-item event listeners)
- Add view-mode aware click delegation for favorites/recent views
- Fix _createFileCard to apply icon_special_class
- Add translateElement(root) for scoped i18n translation
- Replace full-page translatePage() calls with scoped translateElement() or inline t()
- Remove redundant translatePage() calls in shared.js and auth.js
- Remove Alpine.js from Service Worker cache

static/js/multiSelect.js

@@ -284,8 +284,8 @@ const multiSelect = {
                 // Re-wire the select-all checkbox
                 const cb = document.getElementById('select-all-checkbox');
                 if (cb) cb.addEventListener('change', () => this.toggleAll());
-                // Translate restored header
-                if (window.i18n && window.i18n.translatePage) window.i18n.translatePage();
+                // Translate restored header (scoped to list header)
+                if (window.i18n && window.i18n.translateElement) window.i18n.translateElement(listHeader);
             }
 
             // Hide grid bar