Problem

Right-click → "Upload Here" only supports uploading files, not folders. However, drag-and-drop does support folders, creating a UX inconsistency.

Current Behavior

• ✅ Drag & drop: Files AND folders work
• ❌ Right-click menu: Only files work

Expected Behavior

Users should be able to upload folders via the context menu.

Proposed Solution

Add a separate "Upload Folder Here" context menu item that uses webkitdirectory attribute on the file input.

Files to Modify

• src/gui/src/UI/UIDesktop.js - Add directory upload input
• src/gui/src/UI/UIWindow.js - Add context menu item
• src/gui/src/helpers.js - Add upload handler function
• src/gui/src/i18n/translations/*.js - Add translation strings