Fix images on the upload page appearing stretched (having the incorrect aspect ratio) when the image
is enlarged on Safari.
The fix is to set `aspect-ratio` and `height: intrinsic` to ensure the image is the right size. I
have no idea how this works or why it's necessary on Safari.
Fixes https://danbooru.donmai.us/forum_posts/227099.
Redesign the media assets show page to:
* Include sidebar with AI tags and image metadata.
* Include next and previous image buttons.
* Make the image use 100% of the available screen space and to scroll with the window.
* On the upload page, show the video when uploading a video or ugoira.
* On the upload page, show the filesize and resolution beneath the
image, instead of above it.
* On the media asset show page, show the full video or ugoira instead of
just the thumbnail.
