Download button ignores encoded video renditions

[erielpo]

Describe the issue
MediaCMS correctly generates multiple encoded MP4 renditions (e.g. 144p, 256p, 1080p) under media_files/encoded/, and these files are valid and playable. However, the Download button always serves the same file, regardless of the selected resolution.

Even when multiple encoded MP4 files exist on disk with different resolutions and bitrates, the download endpoint appears to always resolve to the original file, ignoring the encoded renditions entirely.

This makes resolution-aware downloads impossible, even though the UI suggests that different qualities are available.

To Reproduce
Steps to reproduce the issue:

1. Deploy MediaCMS using the official Docker image.
2. Upload a video file.
3. Wait until encoding finishes (Celery workers running).
4. Verify that multiple encoded MP4 files exist under media_files/encoded/.
5. Open the video page in the UI.
6. Select different resolutions (e.g. 144p, 256p, 1080p).
7. Click the Download button.
8. Observe that the same file is always downloaded.

Expected behavior
One of the following behaviors would be expected:

• The Download button serves the encoded MP4 file corresponding to the selected resolution, if available

OR

• The UI clearly indicates that downloads are always the original file, regardless of resolution

Currently, the UI suggests resolution-specific downloads, but the backend does not support this behavior.

Actual behavior

• Multiple encoded MP4 files are generated and stored on disk.
• The Download button always serves the same file.
• Resolution selection has no effect on the downloaded file.
• Encoded renditions are never used for downloads.