Re-download is silently skipped when a video is in the download archive but has no database record #909

Youtarr tracks downloads in two places: the database and config/complete.list (the archive yt-dlp uses to skip videos it already has). The channel page and video modal only look at the database to decide if a download is a re-download.

If a video is in the archive but has no database record, it shows as "Not Downloaded", the download dialog doesn't turn on "Allow re-downloading", and yt-dlp skips it. The user just sees a skipped job (or a failed one on 1.86.1) with no hint about what to do.

A user reported this for a video from his first days on Youtarr. The Manual Download paste flow already handles this case because it checks the archive.

To reproduce:

1. Pick a never-downloaded video on a channel page and add youtube <id> to config/complete.list
2. Check its box and click download
3. The dialog opens without "Allow re-downloading" turned on, and the job skips the video

Fix: have the channel page and video modal check the archive too, like the paste flow does, so the dialog turns on "Allow re-downloading" for any selected video that is in the archive.

NOTE: This is not a "big" bug and can't really cause any real problems, it's just annoying for users if they happen to be in this state for old downloads, but should still be fixed.