Feature/video marker

[martintony4all]

This PR allows the search result segments to include a link to the video segment with a second marker. Functions for recently added YouTube videos and direct files. Currently does not have memory of urls of previously added videos from box.

[mileswhiteford]

Hey @martintony4all, The video upload system seems to work for me and the youtube links work well. However there are a few issues I was seeing

The main issue seems to be with the links. On the .m4a box videos, the link to Type: Box (.m4a) videos are download links, instead of opening the actual box page. Not sure if that's intentional.

Second, the Type: Direct (link) videos show blank pages when clicked on.

I’m also not sure if it's necessary to try to rebuild the youtube link if the url wasn't stored, since this could lead to false links being given to the user. Especially with the last check, where any vid with id of 11 is treated as a youtube link, which could cause issues if a box video or some other non-youtube upload has an 11 character long id.

Also, I think yt-dlp should be in requirements.txt and not prompted as a download button if the user doesn't have it installed.

All in all though, I think once the URL issues are fixed this implementation will be really cool.

[martintony4all]

@mileswhiteford valid points:

1. The Box links are meant for the Direct URL option for a single file upload. It previously required the box link to download the audio, but it's now been updated to convert the static box web link of the file into the download format. More info was added to make the distinction clear.

2. The Direct links showing blank pages was caused by internal Azure SAS/blob URLs leaking through as the stored source_url. Fixed so only the original user-facing URL is saved, and internal storage URLs show "no public link" rather than a broken link.

3. the YouTube link reconstruction was removed. If a source URL wasn't stored at index time, the search result now shows "No source URL stored"

4. the yt-dlp was added in requirements.txt, and the install button was removed from the UI. It'll now show an error pointing to requirements.txt if yt-dlp is missing.