Display Upload Date for Files in Web Interface and smartphone apps (and make it sortable)

Currently the Files list only shows the “Modified” column, which reflects the file’s mtime. Since the desktop, mobile and web clients preserve the original mtime of the local file, a file uploaded today can appear as “modified 2 years ago”. There is no way to see when a file was actually added to the server, or to sort by it.

This makes it very hard to find newly uploaded files, especially in shared folders or when receiving older files (photos, documents, exports) from other users.

Proposed solution:
• Add “Uploaded” column to the Files list, sortable like the other columns
• Ideally also add the same sort option in the official mobile apps