Improve upload status panels and hide inactive sections

[xuang7]

Problem statement

Currently, uploads are organized into three panels: Pending, Uploading, and Finished. When there are no active tasks or file changes, the UI still renders all three (empty) panels. The No pending changes message is nested inside the Finished panel, so users don’t immediately see that nothing is pending, which making the interface feel redundant.

Proposed Solution

• Hide inactive panels: Render each status panel only when it has items (count > 0).
• Restore clear empty state: If none of the panels have items, show a top-level notice: No pending changes. (as in the previous implementation).