Fix /stream endpoint serving directory for fileless scenes

[WithoutPants]

Fixes #3526

/stream endpoint now returns 404 if the scene has no files. The File Info tab is also now hidden when the scene has no files.

[DingDongSoLong4]

As it is now, some of the info on the File Info tab isn't explicitly related to the files, like the scene URL (Downloaded From), Stash IDs and the activity tracking info. They will now be hidden when the scene has no files. Activity tracking doesn't really make sense without a file so that's fine, but the scene URL and Stash ID might be set on a fileless scene.

I don't think any of these should really be in a "File Info" tab anyway, so maybe the tab should be renamed to just "Info" or "Scene Info"? It would then make sense to move the Created At and Updated At lines to it as discussed in #2188.

[WithoutPants]

I think that non-file information should be moved out of the current File Info tab, and into the details tab, and that we could potentially split the details tab. For now, I'll revert the file info tab change and hide the stream link instead.