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

src/application/dtos/folder_listing_dto.rs

@@ -0,0 +1,14 @@
+use serde::Serialize;
+
+use super::file_dto::FileDto;
+use super::folder_dto::FolderDto;
+
+/// Combined DTO that returns both sub-folders and files for a given folder
+/// in a single response, eliminating the double-fetch on every navigation.
+#[derive(Debug, Serialize)]
+pub struct FolderListingDto {
+    /// Sub-folders inside the requested folder
+    pub folders: Vec<FolderDto>,
+    /// Files inside the requested folder
+    pub files: Vec<FileDto>,
+}

src/application/dtos/mod.rs

@@ -5,6 +5,7 @@ pub mod display_helpers;
 pub mod favorites_dto;
 pub mod file_dto;
 pub mod folder_dto;
+pub mod folder_listing_dto;
 pub mod i18n_dto;
 pub mod pagination;
 pub mod recent_dto;